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Freezer Alarm
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steve
May 19, 2013, 10:58:23 AM5/19/13
to
Im want to build this circuit.
http://www.discovercircuits.com/PDF-FILES/FREEZERALARM1.pdf
I am a novice at this.
The diagram states that the alarm will go off when the freezer gets to be 0 C.
Actually I think this is too late. Any freezer that goes kaput will hold the temp for perhaps 24 hours before it gets to 0c. By that time the food is now pretty much defrosted. And must really be used up.
How can this circuit be changed to say go off at maybe -3 C. or there abouts.
Thanks all.
P.S.
I cant seem to get any listed parts locally. I want to buy them from SAYAL electronics because they are near me and I can pick them up. But I cant seem to find any of the parts on their web site. I have tried to do comparisons but they dont seem to have any of those parts either. (and maybe IM doing something wrong) I'M sure they have what I need but I just dont have the skill to compare parts, if any Canuck (or other kind person could mach parts that would be great)www.sayal.com
I dont like buy things across the border or on line.
http://www.discovercircuits.com/PDF-FILES/FREEZERALARM1.pdf
I am a novice at this.
The diagram states that the alarm will go off when the freezer gets to be 0 C.
Actually I think this is too late. Any freezer that goes kaput will hold the temp for perhaps 24 hours before it gets to 0c. By that time the food is now pretty much defrosted. And must really be used up.
How can this circuit be changed to say go off at maybe -3 C. or there abouts.
Thanks all.
P.S.
I cant seem to get any listed parts locally. I want to buy them from SAYAL electronics because they are near me and I can pick them up. But I cant seem to find any of the parts on their web site. I have tried to do comparisons but they dont seem to have any of those parts either. (and maybe IM doing something wrong) I'M sure they have what I need but I just dont have the skill to compare parts, if any Canuck (or other kind person could mach parts that would be great)www.sayal.com
I dont like buy things across the border or on line.
Jamie
May 19, 2013, 12:49:44 PM5/19/13
to
|
++-------+
+ |
+ |
.-. |
| |<-+----+
500K | |
'-' Replace the 720K R with this
|
|
.-.
| |
| |500K
'-' To (-) input.
+-----------------+
|
|
|
|
.-.
| |
| | 1 MEG
'-'
|
GND
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
Jamie
steve
May 19, 2013, 10:48:46 PM5/19/13
to
Great thanks.
George Herold
May 20, 2013, 11:50:05 AM5/20/13
to
On May 19, 12:49 pm, Jamie
> Jamie- Hide quoted text -
>
> - Show quoted text -
That will work but you'll have to futz around to set the pot to the
right place.
So the original schematic might have been easier for you to understand
if he used a 361 kohm resistor in the upper arm and the same 499 kohm
resistor in the bottom. Then you just need to look up that
thermistor, find it's resistance at -3 C and plug that resistance into
the place where the 361 kohm is now... Does that make any sense?
George H.
>
> - Show quoted text -
That will work but you'll have to futz around to set the pot to the
right place.
So the original schematic might have been easier for you to understand
if he used a 361 kohm resistor in the upper arm and the same 499 kohm
resistor in the bottom. Then you just need to look up that
thermistor, find it's resistance at -3 C and plug that resistance into
the place where the 361 kohm is now... Does that make any sense?
George H.
amdx
May 20, 2013, 12:07:41 PM5/20/13
to
The LMC 7215 is a surface mount part not easy for him to get.
The LMC7215 is a low power part, 1ua so if his product is battery
powered the LMC7215 may be important.
Mikek
that may be important.
Jamie
May 20, 2013, 7:05:16 PM5/20/13
to
output of a 741/1458 is going to be in the 4+ volt range and the low
output maybe .7 volts, it leaves a narrow window to work with but if you
were to use a MFET as the switch with a Vgs(th) of 2.5V, I guess that
would be fine.
If you don't mind a little sloppy operation I guess it would be fine.
Jamie
Cydrome Leader
May 20, 2013, 6:57:20 PM5/20/13
to
steve <steve...@lycos.com> wrote:
> Im want to build this circuit.
>
> http://www.discovercircuits.com/PDF-FILES/FREEZERALARM1.pdf
>
> I am a novice at this.
>
> The diagram states that the alarm will go off when the freezer gets to be 0 C.
>
> Actually I think this is too late. Any freezer that goes kaput will hold the temp for perhaps 24 hours before it gets to 0c. By that time the food is now pretty much defrosted. And must really be used up.
>
> How can this circuit be changed to say go off at maybe -3 C. or there abouts.
normal freezer temp is -20C. I've not datalogged what the actual temp
> Im want to build this circuit.
>
> http://www.discovercircuits.com/PDF-FILES/FREEZERALARM1.pdf
>
> I am a novice at this.
>
> The diagram states that the alarm will go off when the freezer gets to be 0 C.
>
> Actually I think this is too late. Any freezer that goes kaput will hold the temp for perhaps 24 hours before it gets to 0c. By that time the food is now pretty much defrosted. And must really be used up.
>
> How can this circuit be changed to say go off at maybe -3 C. or there abouts.
swing is in a typical freezer though. The defrost cycle would probably
mess with that depending on where you measure the temp.
Jim Thompson
May 20, 2013, 6:59:04 PM5/20/13
to
combos do that.
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Cydrome Leader
May 20, 2013, 10:25:27 PM5/20/13
to
Jim Thompson <To-Email-Use-Th...@on-my-web-site.com> wrote:
> On Mon, 20 May 2013 22:57:20 +0000 (UTC), Cydrome Leader
> <pres...@MUNGEpanix.com> wrote:
>
>>steve <steve...@lycos.com> wrote:
>>> Im want to build this circuit.
>>>
>>> http://www.discovercircuits.com/PDF-FILES/FREEZERALARM1.pdf
>>>
>>> I am a novice at this.
>>>
>>> The diagram states that the alarm will go off when the freezer gets to be 0 C.
>>>
>>> Actually I think this is too late. Any freezer that goes kaput will hold the temp for perhaps 24 hours before it gets to 0c. By that time the food is now pretty much defrosted. And must really be used up.
>>>
>>> How can this circuit be changed to say go off at maybe -3 C. or there abouts.
>>
>>normal freezer temp is -20C. I've not datalogged what the actual temp
>>swing is in a typical freezer though. The defrost cycle would probably
>>mess with that depending on where you measure the temp.
>>
>
> Good deep freezers don't auto-defrost. Only refrigerator-freezer
> combos do that.
>
> ...Jim Thompson
True, but large restaurant type upright freezers can have defrost cycles.
> On Mon, 20 May 2013 22:57:20 +0000 (UTC), Cydrome Leader
> <pres...@MUNGEpanix.com> wrote:
>
>>steve <steve...@lycos.com> wrote:
>>> Im want to build this circuit.
>>>
>>> http://www.discovercircuits.com/PDF-FILES/FREEZERALARM1.pdf
>>>
>>> I am a novice at this.
>>>
>>> The diagram states that the alarm will go off when the freezer gets to be 0 C.
>>>
>>> Actually I think this is too late. Any freezer that goes kaput will hold the temp for perhaps 24 hours before it gets to 0c. By that time the food is now pretty much defrosted. And must really be used up.
>>>
>>> How can this circuit be changed to say go off at maybe -3 C. or there abouts.
>>
>>normal freezer temp is -20C. I've not datalogged what the actual temp
>>swing is in a typical freezer though. The defrost cycle would probably
>>mess with that depending on where you measure the temp.
>>
>
> Good deep freezers don't auto-defrost. Only refrigerator-freezer
> combos do that.
>
> ...Jim Thompson
There's a gigantic Traulsen freezer at work with a really rediculous 3
digit LED and 4 button "intelligent" controller. It's easy enough to set a
temperature, but what the scrolling cryptic messages mean is beyond even
the service people.
They all say fuck it and just do normal troubleshooting like on any normal
refrigeration device.
F- on the usability and intuitiveness of an "intela-traul" controller.
Jim Thompson
May 20, 2013, 10:36:56 PM5/20/13
to
On Tue, 21 May 2013 02:25:27 +0000 (UTC), Cydrome Leader
Yep. In the kitchen we have a separate SubZero Freezer and SubZero
Refrigerator... big mama's ;-)
Refrigerator... big mama's ;-)
steve
May 21, 2013, 12:37:04 PM5/21/13
to
I'm going to see if I get the parts then will probably get back to the group with questions.
On the defrost thing. Most Deep freezes don't have defrosters I don't think. Those that do only heat the coils behind the plastic wall compartment to remove frost and ice from the coils. This "should" not cool the food, if it did then there would be a problem. This means that the sensor on these type of freezers should be in a small box or something in the freezer, not taped or stuck to the plastic wall of the freezer, as the wall of the freezer can get a little warm with the defrost cycle. Although there is probably places in the compartment that don't have cooling coils.
Thanks.
I'm sure I will be back again.
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