My Mum gave me an old electric furnace. It was originally designed for
cooking ceramic glases ont plates, cups and whatnot, but it should easily
be able to hit 1000 degrees and probably above. The controller is kaput,
however. I'm thinking of replacing it with one of these:
> My Mum gave me an old electric furnace. It was originally designed for
> cooking ceramic glases ont plates, cups and whatnot, but it should easily
> be able to hit 1000 degrees and probably above. The controller is kaput,
> however. I'm thinking of replacing it with one of these:
> Has anyone played with these, or does anyone want to suggest something
> different?
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My osPID arrived today. Pretty nice bit of kit. I'm looking for a safer way
of switching the 240v side of things, rather than wiring to the screw
terminals on the back of the osPID. Jaycar sell this:
It seems like it would be trivial to plug the furnace through one of those
devices and then drive the buttons on the remote from the relay in the
osPID. Set the furnace's controls to full blast and let the osPID handle
the regulation.
Thoughts?
On 26 October 2012 17:26, Lemming . <inert...@gmail.com> wrote:
> Everything I've heard about the OSPID has been pretty complementary.
> On 26 October 2012 17:18, tjhowse <tjho...@gmail.com> wrote:
>> My Mum gave me an old electric furnace. It was originally designed for
>> cooking ceramic glases ont plates, cups and whatnot, but it should easily
>> be able to hit 1000 degrees and probably above. The controller is kaput,
>> however. I'm thinking of replacing it with one of these:
>> Has anyone played with these, or does anyone want to suggest something
>> different?
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> My osPID arrived today. Pretty nice bit of kit. I'm looking for a safer
> way of switching the 240v side of things, rather than wiring to the
> screw terminals on the back of the osPID. Jaycar sell this:
> It seems like it would be trivial to plug the furnace through one of
> those devices and then drive the buttons on the remote from the relay in
> the osPID. Set the furnace's controls to full blast and let the osPID
> handle the regulation.
> Thoughts?
Is it really any safer using a device of questionable quality, compared to knowing you did the job yourself properly?
The osPID seems to be happy to switch 240V@10A so there shouldn't be any problems wiring it up directly (assuming your furnace is less than 10 amps.) Just add another fuse or something if you're really worried, or put it in an earthed metal container so if anything comes loose it'll trip something before it causes problems.
By design the relay load is isolated from the input, and it looks like there's a sufficient air gap on the PCB, so short of a lightning strike there's little chance of the mains bridging over to the low voltage side of the circuit.
Questionable quality? I'm certain that stuff cannot go up for sale in
Australia without meeting standards.
I'm more concerned about having 240v on little screw terminals. With those
remote controlled modules all of the 240v is inside certified 240v
pluggery, entirely separate to the ELV stuff.
On 9 November 2012 15:18, Adam Nielsen <a.niel...@shikadi.net> wrote:
> My osPID arrived today. Pretty nice bit of kit. I'm looking for a safer
>> way of switching the 240v side of things, rather than wiring to the
>> screw terminals on the back of the osPID. Jaycar sell this:
>> It seems like it would be trivial to plug the furnace through one of
>> those devices and then drive the buttons on the remote from the relay in
>> the osPID. Set the furnace's controls to full blast and let the osPID
>> handle the regulation.
>> Thoughts?
> Is it really any safer using a device of questionable quality, compared to
> knowing you did the job yourself properly?
> The osPID seems to be happy to switch 240V@10A so there shouldn't be any
> problems wiring it up directly (assuming your furnace is less than 10
> amps.) Just add another fuse or something if you're really worried, or put
> it in an earthed metal container so if anything comes loose it'll trip
> something before it causes problems.
> By design the relay load is isolated from the input, and it looks like
> there's a sufficient air gap on the PCB, so short of a lightning strike
> there's little chance of the mains bridging over to the low voltage side of
> the circuit.
> Cheers,
> Adam.
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You can actually put 240V on surprisingly small connectors, but only for
low currents (which is the real restriction). Instead your best bet is to
drive an appropriately rated SSR from the OSPID digital output, which then
switches your live rail.
> Questionable quality? I'm certain that stuff cannot go up for sale in
> Australia without meeting standards.
> I'm more concerned about having 240v on little screw terminals. With those
> remote controlled modules all of the 240v is inside certified 240v
> pluggery, entirely separate to the ELV stuff.
> On 9 November 2012 15:18, Adam Nielsen <a.niel...@shikadi.net> wrote:
>> My osPID arrived today. Pretty nice bit of kit. I'm looking for a safer
>>> way of switching the 240v side of things, rather than wiring to the
>>> screw terminals on the back of the osPID. Jaycar sell this:
>>> It seems like it would be trivial to plug the furnace through one of
>>> those devices and then drive the buttons on the remote from the relay in
>>> the osPID. Set the furnace's controls to full blast and let the osPID
>>> handle the regulation.
>>> Thoughts?
>> Is it really any safer using a device of questionable quality, compared
>> to knowing you did the job yourself properly?
>> The osPID seems to be happy to switch 240V@10A so there shouldn't be any
>> problems wiring it up directly (assuming your furnace is less than 10
>> amps.) Just add another fuse or something if you're really worried, or put
>> it in an earthed metal container so if anything comes loose it'll trip
>> something before it causes problems.
>> By design the relay load is isolated from the input, and it looks like
>> there's a sufficient air gap on the PCB, so short of a lightning strike
>> there's little chance of the mains bridging over to the low voltage side of
>> the circuit.
>> Cheers,
>> Adam.
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Apparently the screw terminal block they use is HB611B, which has a claimed
rating of 300V 20A. So you probably could wire directly to the OSPID safely
(as long as it's mounted in an appropriate enclosure.)
- James
On 9 November 2012 15:57, James Churchill <pel...@gmail.com> wrote:
> You can actually put 240V on surprisingly small connectors, but only for
> low currents (which is the real restriction). Instead your best bet is to
> drive an appropriately rated SSR from the OSPID digital output, which then
> switches your live rail.
> On 9 November 2012 15:37, tjhowse <tjho...@gmail.com> wrote:
>> Questionable quality? I'm certain that stuff cannot go up for sale in
>> Australia without meeting standards.
>> I'm more concerned about having 240v on little screw terminals. With
>> those remote controlled modules all of the 240v is inside certified 240v
>> pluggery, entirely separate to the ELV stuff.
>> On 9 November 2012 15:18, Adam Nielsen <a.niel...@shikadi.net> wrote:
>>> My osPID arrived today. Pretty nice bit of kit. I'm looking for a safer
>>>> way of switching the 240v side of things, rather than wiring to the
>>>> screw terminals on the back of the osPID. Jaycar sell this:
>>>> It seems like it would be trivial to plug the furnace through one of
>>>> those devices and then drive the buttons on the remote from the relay in
>>>> the osPID. Set the furnace's controls to full blast and let the osPID
>>>> handle the regulation.
>>>> Thoughts?
>>> Is it really any safer using a device of questionable quality, compared
>>> to knowing you did the job yourself properly?
>>> The osPID seems to be happy to switch 240V@10A so there shouldn't be
>>> any problems wiring it up directly (assuming your furnace is less than 10
>>> amps.) Just add another fuse or something if you're really worried, or put
>>> it in an earthed metal container so if anything comes loose it'll trip
>>> something before it causes problems.
>>> By design the relay load is isolated from the input, and it looks like
>>> there's a sufficient air gap on the PCB, so short of a lightning strike
>>> there's little chance of the mains bridging over to the low voltage side of
>>> the circuit.
>>> Cheers,
>>> Adam.
>>> --
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> Questionable quality? I'm certain that stuff cannot go up for sale in
> Australia without meeting standards.
I've seen a lot of things for sale at the cheap end of the market that were very badly made. It works, and it probably meets the standards, but you wouldn't want one in your home. At that price it's probably fine, but my point was it's not going to be any better than using the screw terminals properly.
> I'm more concerned about having 240v on little screw terminals. With
> those remote controlled modules all of the 240v is inside certified 240v
> pluggery, entirely separate to the ELV stuff.
What's wrong with screw terminals? Lots of stuff uses them, and providing you do up the screws properly they're pretty reliable. It looks like the osPID is meant to mount inside an industry standard cabinet anyway where the terminals aren't exposed.
If you really don't like them, you could desolder the terminals and solder some wires up to a power point instead. Of course the wires attach to the power point at screw terminals... ;-)
Don't get me wrong, I have nothing against the remote control idea, it just seems like a lot more effort than you need.
I cracked the furnace open tonight and found that there was a gigantic
bakelite contactor in the back of it. I should be able to drive that pretty
safely.
On 9 November 2012 16:14, Adam Nielsen <a.niel...@shikadi.net> wrote:
> Questionable quality? I'm certain that stuff cannot go up for sale in
>> Australia without meeting standards.
> I've seen a lot of things for sale at the cheap end of the market that
> were very badly made. It works, and it probably meets the standards, but
> you wouldn't want one in your home. At that price it's probably fine, but
> my point was it's not going to be any better than using the screw terminals
> properly.
> I'm more concerned about having 240v on little screw terminals. With
>> those remote controlled modules all of the 240v is inside certified 240v
>> pluggery, entirely separate to the ELV stuff.
> What's wrong with screw terminals? Lots of stuff uses them, and providing
> you do up the screws properly they're pretty reliable. It looks like the
> osPID is meant to mount inside an industry standard cabinet anyway where
> the terminals aren't exposed.
> If you really don't like them, you could desolder the terminals and solder
> some wires up to a power point instead. Of course the wires attach to the
> power point at screw terminals... ;-)
> Don't get me wrong, I have nothing against the remote control idea, it
> just seems like a lot more effort than you need.
> Cheers,
> Adam.
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I'd be worried about adding unnecessary complication to a device which can
burn things down - namely a device which requires batteries and a
successful wireless connection to work :S
James
On 9 November 2012 17:52, tjhowse <tjho...@gmail.com> wrote:
> I cracked the furnace open tonight and found that there was a gigantic
> bakelite contactor in the back of it. I should be able to drive that pretty
> safely.
> On 9 November 2012 16:14, Adam Nielsen <a.niel...@shikadi.net> wrote:
>> Questionable quality? I'm certain that stuff cannot go up for sale in
>>> Australia without meeting standards.
>> I've seen a lot of things for sale at the cheap end of the market that
>> were very badly made. It works, and it probably meets the standards, but
>> you wouldn't want one in your home. At that price it's probably fine, but
>> my point was it's not going to be any better than using the screw terminals
>> properly.
>> I'm more concerned about having 240v on little screw terminals. With
>>> those remote controlled modules all of the 240v is inside certified 240v
>>> pluggery, entirely separate to the ELV stuff.
>> What's wrong with screw terminals? Lots of stuff uses them, and
>> providing you do up the screws properly they're pretty reliable. It looks
>> like the osPID is meant to mount inside an industry standard cabinet anyway
>> where the terminals aren't exposed.
>> If you really don't like them, you could desolder the terminals and
>> solder some wires up to a power point instead. Of course the wires attach
>> to the power point at screw terminals... ;-)
>> Don't get me wrong, I have nothing against the remote control idea, it
>> just seems like a lot more effort than you need.
>> Cheers,
>> Adam.
>> --
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I had a switching Powerboard purchased from Jaycar.
I tossed it out because the transformer started to melt the plastic.
So yes you get what you pay for.
I have looked into getting devices certified under Australian law, unless
you have a endless bucket if money or a good friend don't go there..
On Saturday, November 10, 2012, James Hodgkinson wrote:
> I'd be worried about adding unnecessary complication to a device which can
> burn things down - namely a device which requires batteries and a
> successful wireless connection to work :S
> James
> On 9 November 2012 17:52, tjhowse <tjho...@gmail.com <javascript:_e({},
> 'cvml', 'tjho...@gmail.com');>> wrote:
>> I cracked the furnace open tonight and found that there was a gigantic
>> bakelite contactor in the back of it. I should be able to drive that pretty
>> safely.
>> On 9 November 2012 16:14, Adam Nielsen <a.niel...@shikadi.net<javascript:_e({}, 'cvml', 'a.niel...@shikadi.net');>
>> > wrote:
>>> Questionable quality? I'm certain that stuff cannot go up for sale in
>>>> Australia without meeting standards.
>>> I've seen a lot of things for sale at the cheap end of the market that
>>> were very badly made. It works, and it probably meets the standards, but
>>> you wouldn't want one in your home. At that price it's probably fine, but
>>> my point was it's not going to be any better than using the screw terminals
>>> properly.
>>> I'm more concerned about having 240v on little screw terminals. With
>>>> those remote controlled modules all of the 240v is inside certified 240v
>>>> pluggery, entirely separate to the ELV stuff.
>>> What's wrong with screw terminals? Lots of stuff uses them, and
>>> providing you do up the screws properly they're pretty reliable. It looks
>>> like the osPID is meant to mount inside an industry standard cabinet anyway
>>> where the terminals aren't exposed.
>>> If you really don't like them, you could desolder the terminals and
>>> solder some wires up to a power point instead. Of course the wires attach
>>> to the power point at screw terminals... ;-)
>>> Don't get me wrong, I have nothing against the remote control idea, it
>>> just seems like a lot more effort than you need.
>>> Cheers,
>>> Adam.
>>> --
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It depends on how you want to control the heat if you want better control
use a SSR then you can drive it directly from 5vdc and use PID control if
you wish. It would also be quiet. This is how I control the 240v heatbed on
my 3d printer. If you are worried about safety I can have a look at it for
you if you like.
On Sat, Nov 10, 2012 at 12:16 AM, Luke Hovington <lu...@hovo.id.au> wrote:
> I had a switching Powerboard purchased from Jaycar.
> I tossed it out because the transformer started to melt the plastic.
> So yes you get what you pay for.
> I have looked into getting devices certified under Australian law, unless
> you have a endless bucket if money or a good friend don't go there..
> On Saturday, November 10, 2012, James Hodgkinson wrote:
>> I'd be worried about adding unnecessary complication to a device which
>> can burn things down - namely a device which requires batteries and a
>> successful wireless connection to work :S
>> James
>> On 9 November 2012 17:52, tjhowse <tjho...@gmail.com> wrote:
>>> I cracked the furnace open tonight and found that there was a gigantic
>>> bakelite contactor in the back of it. I should be able to drive that pretty
>>> safely.
>>> On 9 November 2012 16:14, Adam Nielsen <a.niel...@shikadi.net> wrote:
>>>> Questionable quality? I'm certain that stuff cannot go up for sale in
>>>>> Australia without meeting standards.
>>>> I've seen a lot of things for sale at the cheap end of the market that
>>>> were very badly made. It works, and it probably meets the standards, but
>>>> you wouldn't want one in your home. At that price it's probably fine, but
>>>> my point was it's not going to be any better than using the screw terminals
>>>> properly.
>>>> I'm more concerned about having 240v on little screw terminals. With
>>>>> those remote controlled modules all of the 240v is inside certified
>>>>> 240v
>>>>> pluggery, entirely separate to the ELV stuff.
>>>> What's wrong with screw terminals? Lots of stuff uses them, and
>>>> providing you do up the screws properly they're pretty reliable. It looks
>>>> like the osPID is meant to mount inside an industry standard cabinet anyway
>>>> where the terminals aren't exposed.
>>>> If you really don't like them, you could desolder the terminals and
>>>> solder some wires up to a power point instead. Of course the wires attach
>>>> to the power point at screw terminals... ;-)
>>>> Don't get me wrong, I have nothing against the remote control idea, it
>>>> just seems like a lot more effort than you need.
>>>> Cheers,
>>>> Adam.
>>>> --
>>>> You received this message because you are subscribed to the Google
>>>> Groups "hackerspace_brisbane" group.
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>>>> googlegroups.com.
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>>>> .
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Yeah. I'd replace that contactor with an SSR like Jimmy said. Much quieter
when switching. Much finer grained control and easier to drive with a
micro. Also those old bakelite blocks have a nasty habit if shattering when
you least expect it.
On 09/11/2012, at 17:53, tjhowse <tjho...@gmail.com> wrote:
I cracked the furnace open tonight and found that there was a gigantic
bakelite contactor in the back of it. I should be able to drive that pretty
safely.
On 9 November 2012 16:14, Adam Nielsen <a.niel...@shikadi.net> wrote:
> Questionable quality? I'm certain that stuff cannot go up for sale in
>> Australia without meeting standards.
> I've seen a lot of things for sale at the cheap end of the market that
> were very badly made. It works, and it probably meets the standards, but
> you wouldn't want one in your home. At that price it's probably fine, but
> my point was it's not going to be any better than using the screw terminals
> properly.
> I'm more concerned about having 240v on little screw terminals. With
>> those remote controlled modules all of the 240v is inside certified 240v
>> pluggery, entirely separate to the ELV stuff.
> What's wrong with screw terminals? Lots of stuff uses them, and providing
> you do up the screws properly they're pretty reliable. It looks like the
> osPID is meant to mount inside an industry standard cabinet anyway where
> the terminals aren't exposed.
> If you really don't like them, you could desolder the terminals and solder
> some wires up to a power point instead. Of course the wires attach to the
> power point at screw terminals... ;-)
> Don't get me wrong, I have nothing against the remote control idea, it
> just seems like a lot more effort than you need.
> Cheers,
> Adam.
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The system has a heap of inertia, and the osPID is designed for bang-bang
control. For the hassle involved in replacing components and writing the
code to do analogue proportional control I don't think I'd see a
commensurate increase in performance of the system.
Thanks for the offer of the safety check Jimmy. I might take you up on that
when I bring it into the space sometime.
On 10 November 2012 08:57, Lemming . <inert...@gmail.com> wrote:
> Yeah. I'd replace that contactor with an SSR like Jimmy said. Much quieter
> when switching. Much finer grained control and easier to drive with a
> micro. Also those old bakelite blocks have a nasty habit if shattering when
> you least expect it.
> On 09/11/2012, at 17:53, tjhowse <tjho...@gmail.com> wrote:
> I cracked the furnace open tonight and found that there was a gigantic
> bakelite contactor in the back of it. I should be able to drive that pretty
> safely.
> On 9 November 2012 16:14, Adam Nielsen <a.niel...@shikadi.net> wrote:
>> Questionable quality? I'm certain that stuff cannot go up for sale in
>>> Australia without meeting standards.
>> I've seen a lot of things for sale at the cheap end of the market that
>> were very badly made. It works, and it probably meets the standards, but
>> you wouldn't want one in your home. At that price it's probably fine, but
>> my point was it's not going to be any better than using the screw terminals
>> properly.
>> I'm more concerned about having 240v on little screw terminals. With
>>> those remote controlled modules all of the 240v is inside certified 240v
>>> pluggery, entirely separate to the ELV stuff.
>> What's wrong with screw terminals? Lots of stuff uses them, and
>> providing you do up the screws properly they're pretty reliable. It looks
>> like the osPID is meant to mount inside an industry standard cabinet anyway
>> where the terminals aren't exposed.
>> If you really don't like them, you could desolder the terminals and
>> solder some wires up to a power point instead. Of course the wires attach
>> to the power point at screw terminals... ;-)
>> Don't get me wrong, I have nothing against the remote control idea, it
>> just seems like a lot more effort than you need.
>> Cheers,
>> Adam.
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On Saturday, November 10, 2012 12:09:54 PM UTC+11, tjhowse wrote:
> The system has a heap of inertia, and the osPID is designed for bang-bang > control. For the hassle involved in replacing components and writing the > code to do analogue proportional control I don't think I'd see a > commensurate increase in performance of the system.
It's a shame that they keep commonly calling these things "PID controllers", both osPID and the commercial-off-the-shelf versions, when they're not.
As the osPID website says:
To decide whether you need to use the on board relay or an external SSR depends on the following requirements:
- Do you need the osPID unit and the load voltage to be optically isolated? - Is the load current exceed that of the on board relay? - Do you have some allergy towards relay clicking sound?
If the furnace current is less than 10A @ 240VAC, then you can just use the internal relay inside the osPID. That's what it's there for. It's completely safe to use it - but a device like osPID is not intended to be standalone, it is intended to be inside an enclosure so it's safe.
If you really don't want audible relay clicking, you can use an external SSR. But it's hard to get SSRs to behave themselves at high load currents without getting very hot, better to use a relay. Or a higher-current external relay if the internal 10A relay is not sufficient.
Basically, the very important basic piece of information we haven't yet established here is the furnace current.
> On Saturday, November 10, 2012 12:09:54 PM UTC+11, tjhowse wrote:
>> The system has a heap of inertia, and the osPID is designed for bang-bang
>> control. For the hassle involved in replacing components and writing the
>> code to do analogue proportional control I don't think I'd see a
>> commensurate increase in performance of the system.
> It's a shame that they keep commonly calling these things "PID
> controllers", both osPID and the commercial-off-the-shelf versions, when
> they're not.
> As the osPID website says:
> To decide whether you need to use the on board relay or an external SSR
> depends on the following requirements:
> - Do you need the osPID unit and the load voltage to be optically
> isolated?
> - Is the load current exceed that of the on board relay?
> - Do you have some allergy towards relay clicking sound?
> If the furnace current is less than 10A @ 240VAC, then you can just use
> the internal relay inside the osPID. That's what it's there for. It's
> completely safe to use it - but a device like osPID is not intended to be
> standalone, it is intended to be inside an enclosure so it's safe.
> If you really don't want audible relay clicking, you can use an external
> SSR. But it's hard to get SSRs to behave themselves at high load currents
> without getting very hot, better to use a relay. Or a higher-current
> external relay if the internal 10A relay is not sufficient.
> Basically, the very important basic piece of information we haven't yet
> established here is the furnace current.
> To post to this group, send email to hackerspace_brisbane@googlegroups.com
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I think he's claiming that a PID controller is defined by having an
analogue output, which is incorrect. It is running a PID control loop in
the firmware, so it's a PID controller. The fact that there isn't an
analogue output board yet (just a digital bang-bang one) doesn't change
that.
- James
On 10 November 2012 12:47, tjhowse <tjho...@gmail.com> wrote:
> On 10 November 2012 12:44, Luke Weston <reindeerfloti...@gmail.com> wrote:
>> On Saturday, November 10, 2012 12:09:54 PM UTC+11, tjhowse wrote:
>>> The system has a heap of inertia, and the osPID is designed for
>>> bang-bang control. For the hassle involved in replacing components and
>>> writing the code to do analogue proportional control I don't think I'd see
>>> a commensurate increase in performance of the system.
>> It's a shame that they keep commonly calling these things "PID
>> controllers", both osPID and the commercial-off-the-shelf versions, when
>> they're not.
>> As the osPID website says:
>> To decide whether you need to use the on board relay or an external SSR
>> depends on the following requirements:
>> - Do you need the osPID unit and the load voltage to be optically
>> isolated?
>> - Is the load current exceed that of the on board relay?
>> - Do you have some allergy towards relay clicking sound?
>> If the furnace current is less than 10A @ 240VAC, then you can just use
>> the internal relay inside the osPID. That's what it's there for. It's
>> completely safe to use it - but a device like osPID is not intended to be
>> standalone, it is intended to be inside an enclosure so it's safe.
>> If you really don't want audible relay clicking, you can use an external
>> SSR. But it's hard to get SSRs to behave themselves at high load currents
>> without getting very hot, better to use a relay. Or a higher-current
>> external relay if the internal 10A relay is not sufficient.
>> Basically, the very important basic piece of information we haven't yet
>> established here is the furnace current.
>> To post to this group, send email to
>> hackerspace_brisbane@googlegroups.com.
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>> hackerspace_brisbane+unsubscribe@googlegroups.com.
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>> http://groups.google.com/group/hackerspace_brisbane?hl=en.
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Right, I'd define a PID-controlled-system to have a completely analog feedback loop between the system that you're controlling (say the temperature in a furnace, the temperature measure feedback, and the control of the electrical power input into the heater, for example by phase angle control of a triac.
On Saturday, 10 November 2012 13:51:25 UTC+11, pelrun wrote:
> I think he's claiming that a PID controller is defined by having an > analogue output, which is incorrect. It is running a PID control loop in > the firmware, so it's a PID controller. The fact that there isn't an > analogue output board yet (just a digital bang-bang one) doesn't change > that.
> - James
> On 10 November 2012 12:47, tjhowse <tjh...@gmail.com <javascript:>> wrote:
>> What makes you say it's not a PID controller?
>> On 10 November 2012 12:44, Luke Weston <reindeer...@gmail.com<javascript:> >> > wrote:
>>> On Saturday, November 10, 2012 12:09:54 PM UTC+11, tjhowse wrote:
>>>> The system has a heap of inertia, and the osPID is designed for >>>> bang-bang control. For the hassle involved in replacing components and >>>> writing the code to do analogue proportional control I don't think I'd see >>>> a commensurate increase in performance of the system.
>>> It's a shame that they keep commonly calling these things "PID >>> controllers", both osPID and the commercial-off-the-shelf versions, when >>> they're not.
>>> As the osPID website says:
>>> To decide whether you need to use the on board relay or an external SSR >>> depends on the following requirements:
>>> - Do you need the osPID unit and the load voltage to be optically >>> isolated? >>> - Is the load current exceed that of the on board relay? >>> - Do you have some allergy towards relay clicking sound?
>>> If the furnace current is less than 10A @ 240VAC, then you can just use >>> the internal relay inside the osPID. That's what it's there for. It's >>> completely safe to use it - but a device like osPID is not intended to be >>> standalone, it is intended to be inside an enclosure so it's safe.
>>> If you really don't want audible relay clicking, you can use an external >>> SSR. But it's hard to get SSRs to behave themselves at high load currents >>> without getting very hot, better to use a relay. Or a higher-current >>> external relay if the internal 10A relay is not sufficient.
>>> Basically, the very important basic piece of information we haven't yet >>> established here is the furnace current.
>>> To post to this group, send email to hackerspac...@googlegroups.com<javascript:> >>> . >>> To unsubscribe from this group, send email to >>> hackerspace_brisbane+unsubscribe@googlegroups.com <javascript:>. >>> For more options, visit this group at >>> http://groups.google.com/group/hackerspace_brisbane?hl=en.
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> Right, I'd define a PID-controlled-system to have a completely analog
> feedback loop between the system that you're controlling (say the
> temperature in a furnace, the temperature measure feedback, and the control
> of the electrical power input into the heater, for example by phase angle
> control of a triac.
> On Saturday, 10 November 2012 13:51:25 UTC+11, pelrun wrote:
>> I think he's claiming that a PID controller is defined by having an
>> analogue output, which is incorrect. It is running a PID control loop in
>> the firmware, so it's a PID controller. The fact that there isn't an
>> analogue output board yet (just a digital bang-bang one) doesn't change
>> that.
>> - James
>> On 10 November 2012 12:47, tjhowse <tjh...@gmail.com> wrote:
>>> What makes you say it's not a PID controller?
>>> On 10 November 2012 12:44, Luke Weston <reindeer...@gmail.com> wrote:
>>>> On Saturday, November 10, 2012 12:09:54 PM UTC+11, tjhowse wrote:
>>>>> The system has a heap of inertia, and the osPID is designed for
>>>>> bang-bang control. For the hassle involved in replacing components and
>>>>> writing the code to do analogue proportional control I don't think I'd see
>>>>> a commensurate increase in performance of the system.
>>>> It's a shame that they keep commonly calling these things "PID
>>>> controllers", both osPID and the commercial-off-the-shelf versions, when
>>>> they're not.
>>>> As the osPID website says:
>>>> To decide whether you need to use the on board relay or an external SSR
>>>> depends on the following requirements:
>>>> - Do you need the osPID unit and the load voltage to be optically
>>>> isolated?
>>>> - Is the load current exceed that of the on board relay?
>>>> - Do you have some allergy towards relay clicking sound?
>>>> If the furnace current is less than 10A @ 240VAC, then you can just use
>>>> the internal relay inside the osPID. That's what it's there for. It's
>>>> completely safe to use it - but a device like osPID is not intended to be
>>>> standalone, it is intended to be inside an enclosure so it's safe.
>>>> If you really don't want audible relay clicking, you can use an
>>>> external SSR. But it's hard to get SSRs to behave themselves at high load
>>>> currents without getting very hot, better to use a relay. Or a
>>>> higher-current external relay if the internal 10A relay is not sufficient.
>>>> Basically, the very important basic piece of information we haven't yet
>>>> established here is the furnace current.
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Wouldn't be a chance you could take a picture of the inside for me. I'm just interested how they have positioned the heating element into the chamber, and what heating element they are using. Not gotten the chance to fiddle with one myself you see ;)
> I don't think you know what a PID loop is or does.
> On 10 November 2012 17:18, Luke Weston <reindeerfloti...@gmail.com> wrote:
>> Right, I'd define a PID-controlled-system to have a completely analog
>> feedback loop between the system that you're controlling (say the
>> temperature in a furnace, the temperature measure feedback, and the control
>> of the electrical power input into the heater, for example by phase angle
>> control of a triac.
>> On Saturday, 10 November 2012 13:51:25 UTC+11, pelrun wrote:
>>> I think he's claiming that a PID controller is defined by having an
>>> analogue output, which is incorrect. It is running a PID control loop in
>>> the firmware, so it's a PID controller. The fact that there isn't an
>>> analogue output board yet (just a digital bang-bang one) doesn't change
>>> that.
>>> - James
>>> On 10 November 2012 12:47, tjhowse <tjh...@gmail.com> wrote:
>>>> What makes you say it's not a PID controller?
>>>> On 10 November 2012 12:44, Luke Weston <reindeer...@gmail.com> wrote:
>>>>> On Saturday, November 10, 2012 12:09:54 PM UTC+11, tjhowse wrote:
>>>>>> The system has a heap of inertia, and the osPID is designed for
>>>>>> bang-bang control. For the hassle involved in replacing components and
>>>>>> writing the code to do analogue proportional control I don't think I'd see
>>>>>> a commensurate increase in performance of the system.
>>>>> It's a shame that they keep commonly calling these things "PID
>>>>> controllers", both osPID and the commercial-off-the-shelf versions, when
>>>>> they're not.
>>>>> As the osPID website says:
>>>>> To decide whether you need to use the on board relay or an external
>>>>> SSR depends on the following requirements:
>>>>> - Do you need the osPID unit and the load voltage to be optically
>>>>> isolated?
>>>>> - Is the load current exceed that of the on board relay?
>>>>> - Do you have some allergy towards relay clicking sound?
>>>>> If the furnace current is less than 10A @ 240VAC, then you can just
>>>>> use the internal relay inside the osPID. That's what it's there for. It's
>>>>> completely safe to use it - but a device like osPID is not intended to be
>>>>> standalone, it is intended to be inside an enclosure so it's safe.
>>>>> If you really don't want audible relay clicking, you can use an
>>>>> external SSR. But it's hard to get SSRs to behave themselves at high load
>>>>> currents without getting very hot, better to use a relay. Or a
>>>>> higher-current external relay if the internal 10A relay is not sufficient.
>>>>> Basically, the very important basic piece of information we haven't
>>>>> yet established here is the furnace current.
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On Saturday, 10 November 2012 18:29:31 UTC+11, tjhowse wrote:
> So a PID controller can't be implemented in digital logic, by your > reasoning?
Sure, you can and routinely do have PIDs implemented in digital machines, of course... with some sort of ADC and DAC between the PID algorithm in the digital machine and the analog (physical) system. So all such systems are subject to some (negligible in practice) discretisation error.
More generally, calculus isn't usually implemented exactly in a digital machine... only numerical approximation methods.
Then it wouldn't be a digital input or output then would it. They would be
analog in the physical world. They might not be as accurate as the ones you
describe buy they are still a closed loop system just like a normal house
hold oven is PID controlled in a closed loop.
On Sat, Nov 10, 2012 at 8:03 PM, Luke Weston <reindeerfloti...@gmail.com>wrote:
> On Saturday, 10 November 2012 18:29:31 UTC+11, tjhowse wrote:
>> So a PID controller can't be implemented in digital logic, by your
>> reasoning?
> Sure, you can and routinely do have PIDs implemented in digital machines,
> of course... with some sort of ADC and DAC between the PID algorithm in the
> digital machine and the analog (physical) system.
> So all such systems are subject to some (negligible in practice)
> discretisation error.
> More generally, calculus isn't usually implemented exactly in a digital
> machine... only numerical approximation methods.
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For those watching from the sidelines: The osPID is not a very mature piece
of kit. It's functional, but barely that. I can't comment too much on the
hardware side of things, as I suspect the problems I'm having are
implementation-specific, but the software is pretty awful in most respects.
Processing might be OK for quickly producing prototypes, but I feel it's no
good for actual applications. If I weren't busy with about three different
projects of my own I would look at writing a head-end in python, ala
pronterface. The firmware running on the unit is a bit flakey, and doesn't
seem to heed new manually-entered setpoints. The buttons are intermittantly
unresponsive.
On 11 November 2012 09:41, Jimmy Bowler <denomina...@gmail.com> wrote:
> Then it wouldn't be a digital input or output then would it. They would be
> analog in the physical world. They might not be as accurate as the ones you
> describe buy they are still a closed loop system just like a normal house
> hold oven is PID controlled in a closed loop.
> On Sat, Nov 10, 2012 at 8:03 PM, Luke Weston <reindeerfloti...@gmail.com>wrote:
>> On Saturday, 10 November 2012 18:29:31 UTC+11, tjhowse wrote:
>>> So a PID controller can't be implemented in digital logic, by your
>>> reasoning?
>> Sure, you can and routinely do have PIDs implemented in digital machines,
>> of course... with some sort of ADC and DAC between the PID algorithm in the
>> digital machine and the analog (physical) system.
>> So all such systems are subject to some (negligible in practice)
>> discretisation error.
>> More generally, calculus isn't usually implemented exactly in a digital
>> machine... only numerical approximation methods.
>> To post to this group, send email to
>> hackerspace_brisbane@googlegroups.com.
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>> hackerspace_brisbane+unsubscribe@googlegroups.com.
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I guess I should explain why I'm doing all this. Right now I have a test
print, a companion cube about 20mm to a side, embedded in a block of
plaster. I used 200g of PoP, 200g of silica sand and 140g of water. The
sand was quite moist. I attached two sprues to the cube and oriented it
point-down. One sprue went on the top point, another went on the side
point. The side point is for the molten metal to flow in, the top sprue is
for the air to come out.
I've got it in the furnace now with a ceramic pot full of chunks of
aluminium, with a hole in the bottom, positioned over the feeder hole. The
temperature profile I'm using is:
At 450 the PLA burns away, at 1000 the aluminium should flow. Theoretically
I should have an aluminium companion cube.
Things I suspect will go wrong:
I'm using coloured PLA. Pure PLA burns away to water and carbon dioxide.
Coloured PLA leaves a fine ash of the burned colourant. This will probably
lead to some gunk inside the casting, foul up the surface and at worst:
block the feed hole.
The aluminium mightn't flow into the void. When I'm melting aluminium I
usually have to give it a firm poke to break the oxide coating and release
the molten goodness inside. Since this process is hands-off, the aluminium
might not break out of its oxide crust, or might have too high surface
tension to flow down the 3mm diameter feeder tubes.
I'd like to come and see the new space tonight, but I don't yet trust this
furnace enough to not burn my house down.
On 13 November 2012 17:33, tjhowse <tjho...@gmail.com> wrote:
> For those watching from the sidelines: The osPID is not a very mature
> piece of kit. It's functional, but barely that. I can't comment too much on
> the hardware side of things, as I suspect the problems I'm having are
> implementation-specific, but the software is pretty awful in most respects.
> Processing might be OK for quickly producing prototypes, but I feel it's no
> good for actual applications. If I weren't busy with about three different
> projects of my own I would look at writing a head-end in python, ala
> pronterface. The firmware running on the unit is a bit flakey, and doesn't
> seem to heed new manually-entered setpoints. The buttons are intermittantly
> unresponsive.
> On 11 November 2012 09:41, Jimmy Bowler <denomina...@gmail.com> wrote:
>> Then it wouldn't be a digital input or output then would it. They would
>> be analog in the physical world. They might not be as accurate as the ones
>> you describe buy they are still a closed loop system just like a normal
>> house hold oven is PID controlled in a closed loop.
>> On Sat, Nov 10, 2012 at 8:03 PM, Luke Weston <reindeerfloti...@gmail.com>wrote:
>>> On Saturday, 10 November 2012 18:29:31 UTC+11, tjhowse wrote:
>>>> So a PID controller can't be implemented in digital logic, by your
>>>> reasoning?
>>> Sure, you can and routinely do have PIDs implemented in digital
>>> machines, of course... with some sort of ADC and DAC between the PID
>>> algorithm in the digital machine and the analog (physical) system.
>>> So all such systems are subject to some (negligible in practice)
>>> discretisation error.
>>> More generally, calculus isn't usually implemented exactly in a digital
>>> machine... only numerical approximation methods.
>>> To post to this group, send email to
>>> hackerspace_brisbane@googlegroups.com.
>>> To unsubscribe from this group, send email to
>>> hackerspace_brisbane+unsubscribe@googlegroups.com.
>>> For more options, visit this group at
>>> http://groups.google.com/group/hackerspace_brisbane?hl=en.
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