Need glow plug dropping resistor advice!
Mark Fedasiuk~
Hello, all. I have a quick but important question for anyone that can
answer it. Well, its important to me anyway :-).
I have been flying gliders and helies for a few years, and am now starting
with airplanes.
I never had any need for an airplane type starter before since my heli
had a pull start. Since I now bought one, I would like to use the starter
battery to power my glow plug. I don't want to spend yet *another* $20 on
a power panel just for the dropping resistor.
I don't off hand know how much current a glow plug draws, so I don't know
what value, or wattage dropping resistor to use. Does anyone know?
What is the best value of dropping resistor to use with a 12V starter battery
to get a good glow and not blow my glow plugs?
Is a dropping resistor the best way to go? I assume that that is all there
is to it. Maybe if you want to get fancy you could use a current meter and
a potentiometer.
Well, thats all, thanks in advance to anyone who can help.
mark
PS. any good prop reccomendations for an OSmax .46SF (non ABC)?
What about to break in the engine, should I use a smaller pitch?
I'm thinking of trying a 10x8 or an 11x6 to run.
Iskandar Taib
Mark Fedasiuk~ <mfed...@topcat.intel.com> wrote:
>Is a dropping resistor the best way to go? I assume that that is all there
>is to it. Maybe if you want to get fancy you could use a current meter and
>a potentiometer.
Check out the glow plug driver circuits on bigwig.geology.indiana.edu.
Bigwig is acting up big time. I've got to find some FTP server stuff
that works!
These days I use a poor man's version of the GloBee fireplug. A 2 volt
5 AH Gates sealed lead acid battery (used. $3), a cheap meter face
(scrounged off a battery tester), a 1/3 ohm 5 watt dropping resistor
(which also serves as the meter shunt), all put together in a plastic
case from Radio Shack. I charge the cell with a 12 volt wall charger
using a 20 ohm 10 watt resistor (current is about 1/2 amp). One charge
lasts the whole season, and I have two of these things so if one runs
dry I can use the other. Then I go home and charge both.
--
-------------------------------------------------------------------------------
Iskandar Taib | The only thing worse than Peach ala
Internet: NT...@SILVER.UCS.INDIANA.EDU | Frog is Frog ala Peach
Bitnet: NTAIB@IUBACS !
Risto Pirhonen
>These days I use a poor man's version of the GloBee fireplug. A 2 volt
>5 AH Gates sealed lead acid battery (used. $3), a cheap meter face
>(scrounged off a battery tester), a 1/3 ohm 5 watt dropping resistor
>(which also serves as the meter shunt), all put together in a plastic
>case from Radio Shack. I charge the cell with a 12 volt wall charger
>using a 20 ohm 10 watt resistor (current is about 1/2 amp). One charge
>lasts the whole season, and I have two of these things so if one runs
>dry I can use the other. Then I go home and charge both.
The _SMART_ man's version:
Take 4 normal NiCads, connect them parallel ( you get 1.25 volts and LOTS of
current). With short leads this pack will make any plug glow just fine. Will
last long. Easy to charge.
No more burnt plugs !!!!! (I got many of them when using "smart" circuits)
Normal electronics seem to get wild when they get COLD enough. :-(
Risto Pirhonen
Tampere University of Technology
Keskuudessamme on herannyt epäilyjä myös siitä, että liiallisella
työvoimavahvuudella on jotain yhteyttä koneiden suureen määrään
ja että me nälkärajan alapuolella olevalla palkallamme kustannamme
niiden runsaan käytön.
-TIEHA, TVH F A 8, 1969:VI
Iskandar Taib
Risto Pirhonen <rpir...@ruuvi.me.tut.fi> wrote:
>The _SMART_ man's version:
>Take 4 normal NiCads, connect them parallel ( you get 1.25 volts and LOTS of
>current). With short leads this pack will make any plug glow just fine. Will
>last long. Easy to charge.
>No more burnt plugs !!!!! (I got many of them when using "smart" circuits)
>Normal electronics seem to get wild when they get COLD enough. :-(
I used to use four "D" alkaline cells, 2x2 for 3 volts, with a
dropping resistor (all in parallel didn't work as well). Eventually
this grew to 8 D cells, 4x2 for 3 volts. I assembled the pack with
copious amounts of duct tape.
However, I wanted something better, and for my needs the Gates gel
cell was good, because I needed to use long leads (we start our combat
planes standing up) and needed a meter (you want to KNOW if the plug
is dead!).
Mark Fedasiuk~
Hello All. I'm the original poster who asked the question. I seem to
have started a thread, BUT, nobody how has followed up seems to have
actually answered my *seemingly* simple question. Everyone is
talking about the setups they use.
Maybe my initial question was not clear enough so I'll ask it again...
What I need to know is what *current*, not *voltage* a glow plug uses so
I can use my 12V engine starter battery to power the glowplug.
Nicad starters work fine, yes, and I have several, but since I now will
be using a 12V motor cycle battery to power my electric starter I thought
it would be nice to eliminate one battery (the nicad I use for the glow
starter) and run it off the 12V lead acid battery.
So my question was what is a good dropping resistor value for this.
Lots of here know that V=IR, so that If I know the current that the
glow plug will draw at 1.5 Volts, I can calculate the correct resistance
to drop the rest of the voltage (and wattage).
The simplest way to do it is to just throw a resistor in series with
the plug. The drawback is that the voltage to the glow plug will change
depending on how much current the circuit drawing. ie. the plug will
start out at 12V for an instant before it draws current. This is probably
ok. Also I don't know how mucy the battery voltage is going to drop when
I use the starter. I fear if it drops too much that the current to the
glowplug will decrease as soon as I start spinning the prop with the
starter.
Now Does anyone know how they do it in those power panels? Are they just a
simple dropping resistor, or is there a voltage regulator?
I could just go buy a voltage regulator from RADIO SHACK and use that, but
I though that someone could just tell my what works best.
Please, some one MUST have tried to do this in the past.
mark
Iskandar Taib
Lee Raesly <l...@pro-novapple.clark.net> wrote:
>In <2npls3$c...@chnews.intel.com>
>mfed...@topcat.intel.com (Mark Fedasiuk~) writes:
>
> much stuff deleted.
>
>>I don't off hand know how much current a glow plug draws, so I don't know
>>what value, or wattage dropping resistor to use. Does anyone know?
>>
>
>
>A glow plg uses 1.5 volts.
And will draw between 2 and 4 amps.
btw.. the Cox high compression glowhead (as fitted to a Tee Dee) will
need ~ 2 volts for quick starting.
Steven W. Bixby
: Hello All. I'm the original poster who asked the question. I seem to
: have started a thread, BUT, nobody how has followed up seems to have
: actually answered my *seemingly* simple question. Everyone is
: talking about the setups they use.
...
: The simplest way to do it is to just throw a resistor in series with
: the plug. The drawback is that the voltage to the glow plug will change
: depending on how much current the circuit drawing. ie. the plug will
: start out at 12V for an instant before it draws current. This is probably
: ok. Also I don't know how mucy the battery voltage is going to drop when
: I use the starter. I fear if it drops too much that the current to the
: glowplug will decrease as soon as I start spinning the prop with the
: starter.
This IS going to happen. Some of the really old panels just use a big fat
pot to drop the voltage down to where you want it, but as soon as you apply
that starter, the glow gets weak and you're at Catch-22 stage.
: Now Does anyone know how they do it in those power panels? Are they just a
: simple dropping resistor, or is there a voltage regulator?
I don't know about the NEWEST panels, but many of the 'normal' panels
these days use a pulse-type circuit (hey, I'm no EE!) to drive the
glowplug; it just switches it on and off at the full voltage and current
of the battery at a rate that just keeps the plug lit to the correct
level. Mine is an old SonicTronics 'VariPulse' panel that has served me
well for 12 years now. Normally the plug doesn't vary when applying the
starter; when the battery charge is on it's last legs, then the starter
will cause the glow to dim a little.
: I could just go buy a voltage regulator from RADIO SHACK and use that, but
: I though that someone could just tell my what works best.
I suspect that you're not an EE either, or you wouldn't be asking how to
do this. For what they give you, I think a power panel is a good investment.
I have NiStarters, but I usually do not use them, simply because they're
a hassle compared to just plugging into my panel when starting. Also, they
provide you with a meter indicative of the plug's brightness (not
just voltage level), and provide a switched takeoff for an electric pump
(another 'can't live without it now that I have one' feature.)
$30 is a drop in the bucket compared to some of the planes and radios we
buy... why not?
--
-swb- (Steve Bixby, sbi...@crl.com)
Elvis Engineer Doin' It The Cowboy Way
several of us (EEs like myself and others) bandied about. It is worth
looking into. (I think we finally concluded it actually did work.. :-) )
I don't have it handy, or I would just post it for you.
Iskandar?
L.
_____________________________________________________________________________
| Larry E. Cunningham |
____ | %Physical Science Laboratory | _~~_
| | ___\ /~~~| | New Mexico State University | (O)(-)
_:_______|/'(..)`\_______/ | | | Las Cruces, NM USA 88003 | /..\
<_|`````` \__~~__/ USAF ___|_| | la...@psl.nmsu.edu | ==
:\_____(=========,(*),--\__|_/ |----------------------------------------
| \ /---' |"Yeh, Buddy..
| (*) / Mustangs | I've got your COMPUTER!
|____/ Forever | Right HERE!!" (computer THIS!)
____________________________________|________________________________________
Opinions expressed here are CORRECT, and all mine, not PSLs and not NMSUs..
Do NOT use the term FAT around me. I'm NOT fat. I'm gravitationally challenged.
Mark Maiolani
>The third solution, which I think would be cheap and easy would be to
>buy a voltage regulator chip from Radio Shack (as I mentioned in a
>previous post) and just pick the correct resistor ratios in order to
>source a constant current or voltage out if the battery. If I recall
>correctly I can get several amps out of one of those things if I heat
>sink it. I used one in a home brew voltage or current controlled power
>supply I built about 10 or 15 years ago (when I was in highschool) and
>it worked quite nice. Ironically I built that supply to charge the sub-c
>nicad packs for one of my first RC models. Now it seems that my life
>is comming full circle :-).
>So for a couple of bucks I can build a simple circuit to give me a
>constant 1.5 volts sourced off of my 12V battery even if the battery
>drops in voltage under load.
Just remember that if you pump in 12 V to the regulator it will still have to
dissipate the same amount of heat as a plain resistor (assuming a linear
voltage regulator). It might be difficult to keep the reg. at a reasonable
temperature if you use the driver for a long period (the 2A rating of the
regulator is not the problem here). An addition of a series power resistor
before the reg. could be used if the reg. can't handle the power on it's own.
All you would have to do is make sure that the input to the reg is a volt or 2
above the required 2V at full load then.
Mark
Disclaimer : The above views are not necessarily those of my employer.
As usual...
David Svoboda
Mark Fedasiuk~ <mfed...@topcat.intel.com> wrote:
|
|Now Does anyone know how they do it in those power panels? Are they just a
|simple dropping resistor, or is there a voltage regulator?
Well, neither. The Sonic-Tronics power panel that I use actually pulses
a 12 volt square wave to the plug, and has a knob which controls the duty
cycle. This gives some RMS voltage through the plug element.
Years ago there was a design out there called the "Glow Driver" which not
only pulsed 12V to the plug, but varied the duty cycle based on current
flow. Because a glow element changes its resistance based on how much it
is glowing, the simple feedback loop in the Glow-Driver could regulate
the temperature of the plug very accurately, even in the face of extreme
flooding--very good for inverted engines, especially.
I have been trying for a few years to get hold of the original plans for
the Glow Driver, without success. I've even asked Clarence Lee, who
asked me to pass them onto him when I find them. If anyone out there has
any old magazines that have the design, could you let me know? (Yes, I
could design it myself, but feedback systems are tricky, and I'm not that
much of a EE.)
Dave Svoboda, Palatine, IL
Elvis Engineer Doin' It The Cowboy Way
away to drop the voltage has to be dissipated SOMEWHERE and that is the
series pass element.
A far less dissipative method would be to operate in switch mode. The 555
circuits are doing precisely this, with the ON duty cycle adjusted to
provide the average power you want. Although I'm sure someone somewhere
will dispute the point, the glowplug doesn't mind getting short 13.2 volt
pulses as long as the average power isn't exceeded. In addition, the
circuit can be enhanced to adjust duty cycle as the battery voltage drops
off, to compensate. Plus have a pot to set the color of orange you like..
Although the circuit Iskandar had at his ftp site (maybe it's still
there..) used a Darlington transistor pair as the switching element, we
both agreed that a modern power MOSFET would be an ideal element. These
have an ON resistance in the milliohms and an OFF resistance in the
megohms - an ideal switch.
I've been looking through all my mass of junk and I can't seem to find the
circuit, but I'll keep looking..
Good luck to you.
L.
"Yeh, Buddy.. | la...@psl.nmsu.edu (Larry Cunningham)| _~~_
I've got your COMPUTER! | % Physical Science Laboratory | (O)(-)
Right HERE!!" | New Mexico State University | /..\
(computer THIS!) | Las Cruces, New Mexico, USA 88003 | <>
--------------------------------------------------------------------------
Disclaimer: Opinions expressed here are CORRECT, mine, and not PSLs or NMSUs..
Oh sure, we could do it the _easy_ way. But it just wouldn't be the COWBOY WAY.
Robert Neil Whiteman
After reading several of the comments regarding the glow plug
electrical requirements, I thought I would pass on some other
ideas for what they might be worth.
If you have not chosen a 12 volt battery yet, you could build up
this battery by using a series connection of 2 volt, 6 volt or
other voltage batteries. Depending upon your mAhr requirement
[and $ available] NiCads could even be used. This would allow
you to tap the glow plug circuit into a lower voltage connection
and lower the power dissipation requirements of the resistor.
Just recently I purchased a new electronic speed control
(Astroflight #217) for less than $30. This could be used as an
efficient means to power the glow plug circuit when controlled
with a simple PWM circuit (555 chip?). Used ESC's may be cheaper
if you can find one or have one in your junk box.
Regards;
Bob Whiteman
Iskandar Taib
>What I need to know is what *current*, not *voltage* a glow plug uses so
>I can use my 12V engine starter battery to power the glowplug.
As I posted earlier, something between 2 and 4 amps, depending on the
plug. I think you'll need some kind of variable resistor of high
wattage (they're kinda expensive).
>So my question was what is a good dropping resistor value for this.
>Lots of here know that V=IR, so that If I know the current that the
>glow plug will draw at 1.5 Volts, I can calculate the correct resistance
>to drop the rest of the voltage (and wattage).
Problem is that R doesn't remain constant, either for the plug or for
the resistor. A friend of mine tells me you end up with a bad positive
feedback problem that ends up in burned plugs: as the plug heats up
its resistance increases, and the voltage drop across the plug will
similarly increase (since V(p) = 12 * (R(p)/R(tot)), which increases
the power dissipation across the plug element, which makes it hotter
yet.. (I haven't decided whether he's right or not..)
>The simplest way to do it is to just throw a resistor in series with
>the plug. The drawback is that the voltage to the glow plug will change
>depending on how much current the circuit drawing. ie. the plug will
>start out at 12V for an instant before it draws current. This is probably
>ok. Also I don't know how mucy the battery voltage is going to drop when
>I use the starter. I fear if it drops too much that the current to the
>glowplug will decrease as soon as I start spinning the prop with the
>starter.
You actually want to decrease current when the motor starts (though,
of course, this isn't the same thing). The MAIN problem with doing it
with a dropping resistor is that your battery doesn't remain charged
very long..
>Now Does anyone know how they do it in those power panels? Are they just a
>simple dropping resistor, or is there a voltage regulator?
The old ones did. All the newer ones, even the cheap ones from Taiwan,
use a "chopper" - a circuit based on a 555 chip and a power
transistor, much like an electronic speed controller. The big
advantage is that these draw far less current than the old
resistor-based power panels, and don't get really hot.
The more expensive ones (eg. the $50 Goldberg one) use a "smart"
circuit - it supplies more current when the plug is cold and less when
the plug is hot, so the plug element is kept to more or less a
constant temperature. Great for clearing out plugs, and the plug isn't
overheated when the motor starts running.
I stopped using power panels after that one time I had to fly in the
rain..
>I could just go buy a voltage regulator from RADIO SHACK and use that, but
>I though that someone could just tell my what works best.
These also dissipate lots of power, i.e. run hot and waste battery
charge.
Iskandar Taib
Elvis Engineer Doin' It The Cowboy Way <la...@summit.nmsu.edu> wrote:
>Speaking of 555 circuits and such, Iskandar had a circuit some time back which
>several of us (EEs like myself and others) bandied about. It is worth
>looking into. (I think we finally concluded it actually did work.. :-) )
>
>I don't have it handy, or I would just post it for you.
>
>Iskandar?
>L.
I'm having problems with the FTP software.
I tried uploading it to a Unix account last night but it seems to be
in MS-DOS format (^M's everywhere). I'll try to locate a DOS2Unix copy
and do it again tonight so I can mail it out.
Iskandar Taib
>In article <CnswE...@usenet.ucs.indiana.edu>, nt...@silver.ucs.indiana.edu (Iskandar Taib) writes:
>> And will draw between 2 and 4 amps.
>
>Which in turn means that if you're going to use a 12v battery as your
>power source you'll need a 2.625 ohm resistor that can handle about 42 watts..
>I believe that you'll have a hard time finding such a resistor... :-)
>I recently designed a 12v glow driver that uses a bipolar power transistor
>to handle the voltage drop. The current that flows through the glow plug
>is adjustable, and it is short circuit protected.
>The only disadvantage is that I have to use a pretty big heatsink on the
>output transistor... :-(
>But since the circuit is so simple, it is easy to build it, and make it
>work.
Why not 3-4 10 watters in parallel? 4 10 ohm, 10 or 15 watt resistors
would be easy to find. Each would dissipate 10.5 V x 1 amp = 10.5
watts at worst.
The main problem I see is differences between plugs. You WILL need
some adjustability, so one of those 10 ohm resistors could perhaps be
replaced by a 5 ohm resistor in series with a 5 ohm potentiometer, and
you might want to use 12 or 15 ohm resistors instead.
Mark Fedasiuk~
>Your points about series regulators are well taken - the power you throw
>away to drop the voltage has to be dissipated SOMEWHERE and that is the
>series pass element.
>
>A far less dissipative method would be to operate in switch mode. The 555
>circuits are doing precisely this, with the ON duty cycle adjusted to
>provide the average power you want. Although I'm sure someone somewhere
>will dispute the point, the glowplug doesn't mind getting short 13.2 volt
>pulses as long as the average power isn't exceeded. In addition, the
>circuit can be enhanced to adjust duty cycle as the battery voltage drops
>off, to compensate. Plus have a pot to set the color of orange you like..
>
>Although the circuit Iskandar had at his ftp site (maybe it's still
>there..) used a Darlington transistor pair as the switching element, we
>both agreed that a modern power MOSFET would be an ideal element. These
>have an ON resistance in the milliohms and an OFF resistance in the
>megohms - an ideal switch.
>
Thanks to all for the advice. I'm sorry about being a little testy in my
second post, but I got so many replys (at first) without one addressing
my actual question. Shortly thereafter I did recieve several very helpful
replies and thanks to all (you know who you are).
Someone sent me the schematic which Iskandar captured from the FTP site.
That was the one which used a 555 to switch a Darlington pair.
That seemed like the way to go so I built one last night.
I used components and values right off the schematic. The few I didn't
already have I bought at Radio Shack. The only component I couldn't
get there was the PNP power transistor. I just substituted the one and
only PNP power transistor that Radio Shack carried for the TIP105 which
they did not have a cross reference for.
I looked at the specs, and it could handle 15A continuous, and dissapate
150 watts. It also said that it was good for switching applications.
I figured that that would do.
Now to be honest, I *was* planning on saving some money by doing this
by not using a panel meter, current adjust pot,... Just make the
bare bones driver and size the compontents for about a 3 amp drive through
the glow plug. Steve Bixbey pointed out that you get alot for your money
when you buy a power panel from Tower for about $20-$30. He is right.
I have a box of compontents, resistors, caps, pots, transistors, 555's,....
I really only had to buy the power transistor, and the large Diode
to build the basic driver. That would have only cost me a couple of
bucks. But... I got swept up in this whole project thing and went delux.
I bought an $8 panel meter, project box, nice trimmer pots, knobs,...
everything to make it delux. All in all I spent $20 just on parts!
By this time, it was no longer a money issue, I just was just having fun
doing it myself.
Back to the point... I built it on proto board last night, fired it up,
and it worked like a charm! I first had the emitter and collector on the
power transistor reversed so that the NPN switching transistor got really
hot since it had to drive alot more current through the PNP's gate for the
same gain. I quickly figured what the problem was and switched the leads and
bingo!
The cicruit is *nice*. The only thing is that you can hear it! It almost
sounds like the power transistor is making noise at the frequency that
the 555 is oscillating at. Its kind of like a buzzing sound.
Also even though the power transistor is rated 15A, 150Watts, it still
gets hot without a heat sink. I think I'll add one when I breadboard it
tonight.
By the way I used 3 parallel .47 ohm 5W shunt resistors for the meter
shunt which yields about .15 ohms. I calculated I(fs) of the Radio Shack
meter to be 1mA. The meter reads 15V at full scale and has bold markings
at 0,5,10, and 15Volts. I decided to calibrate the meter to be X(.4) so
that each 5V marking corresponds to 2Amps through the glow plug with
3Amps dead in the center of the scale. To do this I needed a 1k trimmer
pot (I used the 15 turn kind) in series with the meter. It worked like a
charm.
Boy I haven't done 'lectronics for awhile now, and it revived the
geek in me :-) :-) :-).
All in all, I have to agree with Steve, your not going to save alot of money
by building your own glow driver circuit, but it is fun and easy!
By the way, as discussed earlier, a MOSFET might be better and dissapate
less heat. Aside from the extra heat (and power), this circuit works
great!!!
Good luck to all if you wish to build it.
If anyone is interested, I'll post the schematc.
mark
Mark Fedasiuk~
>away to drop the voltage has to be dissipated SOMEWHERE and that is the
>series pass element.
>
>A far less dissipative method would be to operate in switch mode. The 555
>circuits are doing precisely this, with the ON duty cycle adjusted to
>provide the average power you want. Although I'm sure someone somewhere
>will dispute the point, the glowplug doesn't mind getting short 13.2 volt
>pulses as long as the average power isn't exceeded. In addition, the
>circuit can be enhanced to adjust duty cycle as the battery voltage drops
>off, to compensate. Plus have a pot to set the color of orange you like..
>
>Although the circuit Iskandar had at his ftp site (maybe it's still
>there..) used a Darlington transistor pair as the switching element, we
>both agreed that a modern power MOSFET would be an ideal element. These
>have an ON resistance in the milliohms and an OFF resistance in the
>megohms - an ideal switch.
>
JWW
I would not use a power panel with 12v battery Yes it works but I blew
3 or 4 plugs when by bumping the adjustment knob and not seeing it. I
bought one of the nistarters that use a sub C battery last year and to
date I am
still using the same plug. I think by now I have paid for the starter
Steven W. Bixby
Although I'm deaf enough to not hear it, most of my friends commented on
how the panel 'sings' when it's busy (SonicTronics VariPulse). So it's
normal for this type of circuit, I believe.
Steven W. Bixby
: Can you guys publish a circuit for MAINTAINING
: Glow plug glow during FLIGHT so that your engine
: wont quit? Needs to be servo controlled so
: that moving to low throttle will activate it..
: I believe Tower Hobbies sells such a
: product, but I'd rather make one myself for
: the fun of it.
There are several commercial products, but most of them must provide a
mechanical switch harness to turn on a sub-C NiCad cell when the throttle
is below some predetermined position.
Typically using a bump or bolt on a servo wheel to press a microswitch,
as well as another 'arming' switch to prevent the cell from lighting the
plug 'off-hours'.
Iskandar Taib
Mark Fedasiuk~ <mfed...@topcat.intel.com> wrote:
>Someone sent me the schematic which Iskandar captured from the FTP site.
>That was the one which used a 555 to switch a Darlington pair.
>That seemed like the way to go so I built one last night.
Out of curiosity - which circuit did you build? There are two on
bigwig - one is relatively simple, and is used by most of the cheaper
power panels - the output on the 555 is used to switch a Darlington
pair, with the duty cycle and frequency of the 555 controlled by some
simple RC circuitry. The other one is quite a bit more complex, and
has a positive feedback element to it - the glowplug is one leg of a
Wheatstone bridge, which "talks to" an op-amp used as a comparator,
which does something to the 555 to turn it on or off or vary the duty
cycle. This one requires a choke, an op amp, and various other things.
It came out of an Australian model magazine (courtesy of Chris
Kaiser). I think the way I drew it I used a IRF511 MOSFET for the
power switch.
Iskandar Taib
I haven't blown plugs with the adjustment knob, but see what a little
rain will do to most power panels..
I also had a nasty pitbox fire once when the glowclip shorted out
against the front of the panel (yes, on many cheap power panels the
front of the panel is HOT!) and the meter shunt melted.
Allan TEO
: RE the Glow driver circuit buzzing...
: Although I'm deaf enough to not hear it, most of my friends commented on
: how the panel 'sings' when it's busy (SonicTronics VariPulse). So it's
: normal for this type of circuit, I believe.
: --
:
Hi,
Can you guys publish a circuit for MAINTAINING
Glow plug glow during FLIGHT so that your engine
wont quit? Needs to be servo controlled so
that moving to low throttle will activate it..
I believe Tower Hobbies sells such a
product, but I'd rather make one myself for
the fun of it.
Regds
Allan
Elvis Engineer Doin' It The Cowboy Way
something works the first time like that, it means you really screwed up
somewhere else.. ;-)
Microphonics is often a problem when you operate a circuit switching
some power at audio frequencies. One solution would be to operate at
higher frequencies. That would require changes in the Rs and Cs
surrounding the 555 timer. I'm sure the glow plug would mind it even
less.. (You still might end up hearing the circuit, however, due to
slow rise times on the output, who knows?)
The power dissipation comes from two things. First, power transistors
aren't optimal switches, even with the current multiplication on the base
of the Darlington configuration. Second, the Darlington configuration
essentially has to double the Vce(sat) [saturation voltage drop] across
two transistors, and there goes your I squared R losses up. Even so,
compared to series regulator, the switching circuit is quite efficient.
A power MOSFET would offer a superior approach, of course, for a few
dollars more.
We need to remind ourselves that we are building a glow driver here,
nothing that REALLY needs be all that exotic. Not that some of us mind
shooting flies with a shotgun.. And look at the fun you had! :-)
Regards,
Elvis Engineer Doin' It The Cowboy Way
>
>I would not use a power panel with 12v battery Yes it works but I blew
>3 or 4 plugs when by bumping the adjustment knob and not seeing it. I
>bought one of the nistarters that use a sub C battery last year and to
>date I am
>still using the same plug. I think by now I have paid for the starter
Iskandar> I haven't blown plugs with the adjustment knob, but see
Iskandar> what a little rain will do to most power panels..
Iskandar> I also had a nasty pitbox fire once when the glowclip
Iskandar> shorted out against the front of the panel (yes, on many
Iskandar> cheap power panels the front of the panel is HOT!) and
Iskandar> the meter shunt melted.
I guess I ought to pull my Tower Power Panel out and give it to some
friendly R/Cer. When I first built my flight box with the power panel, I
thought it was the greatest thing since sliced bread, even though I never
used the electric fuel pump and starter features (CL stunt..). As time
went on, I picked up a hot shot (allegedly for convenience at contests),
and have never looked back on the power panel. The last time I tried to
charge the flight box to get ready for a contest, I discovered that the
battery was dead and dry..
More recently, I've had second thoughts, however, mainly in the interest
of being able to have an easy hookup for an electric starter. After my
flying buddy nicked his finger on a CF prop (I think he tried to reach
THROUGH the prop on a running ST. 60), requiring a visit to the emergency
room and 13 stitches, we started thinking more seriously about SAFETY.
So, we are starting to consider that, manly as it might be to hand prop an
ST. 60 with a CF "knife blade" prop, we might resort to those sissy
electric starters.. :=0 (Plus our rules changed to eliminate those 5
"starting points" and allow electric starters..)
The other thing is, having an adjustable glow driver really can help
sometimes, and its meter gives a very good indication of a blown plug!
Wide variations in plugs can be accommodated. One thing I noticed after
switching to using the hotshot exclusively was that my glow plug life
seemed to decrease, from many months, to many weeks. I think maybe the
hotshot is a little TOO hot for some of the plugs, and this is where the
glow driver with the adjustment is pretty nice.
So, guess I'll keep the silly thing, and get a new battery for it..
L.
"Yeh, Buddy.. | la...@psl.nmsu.edu (Larry Cunningham)| _~~_
I've got your COMPUTER! | % Physical Science Laboratory | (O)(-)
Right HERE!!" | New Mexico State University | /..\
(computer THIS!) | Las Cruces, New Mexico, USA 88003 | <>
--------------------------------------------------------------------------
Disclaimer: Opinions expressed here are CORRECT, mine, and not PSLs or NMSUs..
Tularosa: tullies, roses, lava, white sands, and home of THEM! (atomic ants).
Mark Fedasiuk~
>In article <2o1e08$f...@chnews.intel.com>,
>Mark Fedasiuk~ <mfed...@topcat.intel.com> wrote:
>
>>Someone sent me the schematic which Iskandar captured from the FTP site.
>>That was the one which used a 555 to switch a Darlington pair.
>>That seemed like the way to go so I built one last night.
>
>Out of curiosity - which circuit did you build? There are two on
>bigwig - one is relatively simple, and is used by most of the cheaper
>power panels - the output on the 555 is used to switch a Darlington
>pair, with the duty cycle and frequency of the 555 controlled by some
>simple RC circuitry. The other one is quite a bit more complex, and
>has a positive feedback element to it - the glowplug is one leg of a
>Wheatstone bridge, which "talks to" an op-amp used as a comparator,
>which does something to the 555 to turn it on or off or vary the duty
>cycle. This one requires a choke, an op amp, and various other things.
>It came out of an Australian model magazine (courtesy of Chris
>Kaiser). I think the way I drew it I used a IRF511 MOSFET for the
>power switch.
>
>
I built the first one you described. It was just a simple 555 set up as
oscillator who's output was used to modulate the Darlington pair.
It seems like the second one you described was the "smart" circuit that
someone was just requesting using feedback to keep the current in the
glowplug constant. Do you have a copy of it? Can you post it for us?
I would like to take a look at *that* circuit.
Thanks again Iskandar for drawing the schematics in the first place.
mark
Iskandar Taib
Elvis Engineer Doin' It The Cowboy Way <la...@summit.nmsu.edu> wrote:
>Iskandar> I haven't blown plugs with the adjustment knob, but see
>Iskandar> what a little rain will do to most power panels..
>
>Iskandar> I also had a nasty pitbox fire once when the glowclip
>Iskandar> shorted out against the front of the panel (yes, on many
>Iskandar> cheap power panels the front of the panel is HOT!) and
>Iskandar> the meter shunt melted.
>I guess I ought to pull my Tower Power Panel out and give it to some
>friendly R/Cer. When I first built my flight box with the power panel, I
>thought it was the greatest thing since sliced bread, even though I never
>used the electric fuel pump and starter features (CL stunt..). As time
>went on, I picked up a hot shot (allegedly for convenience at contests),
>and have never looked back on the power panel. The last time I tried to
>charge the flight box to get ready for a contest, I discovered that the
>battery was dead and dry..
What I did the second time I had one of these was make up a plexigass
panel to fit in front of the panel. Back then I built a box; these
days I'd use standoffs. Then one day it got rained on..
>More recently, I've had second thoughts, however, mainly in the interest
>of being able to have an easy hookup for an electric starter. After my
>flying buddy nicked his finger on a CF prop (I think he tried to reach
>THROUGH the prop on a running ST. 60), requiring a visit to the emergency
>room and 13 stitches, we started thinking more seriously about SAFETY.
>
>So, we are starting to consider that, manly as it might be to hand prop an
>ST. 60 with a CF "knife blade" prop, we might resort to those sissy
>electric starters.. :=0 (Plus our rules changed to eliminate those 5
>"starting points" and allow electric starters..)
The FF people have for many years been using setups where the starter
is mounted on a box. Pressure on the starting cone causes the starter
to turn - I think they use a sliding mount, a spring and a
microswitch. The big idea is you stand behind the airplane to start
it. Someone has started selling these commercially for the R/C market.
I guess in this case you'd not want a power panel..
>The other thing is, having an adjustable glow driver really can help
>sometimes, and its meter gives a very good indication of a blown plug!
>Wide variations in plugs can be accommodated. One thing I noticed after
>switching to using the hotshot exclusively was that my glow plug life
>seemed to decrease, from many months, to many weeks. I think maybe the
>hotshot is a little TOO hot for some of the plugs, and this is where the
>glow driver with the adjustment is pretty nice.
The GloBee Fireplug has gotten very popular with the Combat crowd. And
racers like them because they can strap them to their arms.
>So, guess I'll keep the silly thing, and get a new battery for it..
There was someone selling 12 volt gel cells at the Nats last year for
$10.. Maybe he'll be there this yar too! ^_^
Steve Jensen
hear it whistle. :) I also carry a backup rig in case the glow driver
quits. This has only happened once in 12 years. It's just a wire with
a couple car stoplight bulbs for the resisters. It lights everything from
Cox's to Nelsons and Globees.
--
sje...@eis.calstate.edu 8-()
- _ ! Still smokin'.
Iskandar Taib
Steve Jensen <sje...@eis.calstate.edu> wrote:
>For my freeflight field box I use the Sonictronix glow driver. I like to
>hear it whistle. :) I also carry a backup rig in case the glow driver
>quits. This has only happened once in 12 years. It's just a wire with
>a couple car stoplight bulbs for the resisters. It lights everything from
>Cox's to Nelsons and Globees.
Yeah! Why didn't I think of this? I take it the bulbs are in parallel?
I don't think the bulbs pass more than 1 amp each.
By the way - a really cheap and dirty battery charger for 1 or 2 cells
can be made with a 12 volt supply (or charger, if you have one lying
around) and some light bulbs. I think I'll go to this rather than use
resistors - the resistor gets awful hot.
Doug Ingraham
>
>
> Hello All. I'm the original poster who asked the question. I seem to
> have started a thread, BUT, nobody how has followed up seems to have
> actually answered my *seemingly* simple question. Everyone is
> talking about the setups they use.
>
> Maybe my initial question was not clear enough so I'll ask it again...
>
>
> What I need to know is what *current*, not *voltage* a glow plug uses so
> I can use my 12V engine starter battery to power the glowplug.
Normal glow plugs will start motors at between 3 and 4 amps of current.
If you go much more than this, you end up with problems of short plug life
and the motor tending to start backwards.
< text deleted >
>
> Now Does anyone know how they do it in those power panels? Are they just a
> simple dropping resistor, or is there a voltage regulator?
The power panels use a fet to control a pwm type constant current regulator.
You set the current and the control system keeps the current constant. In
general this is the way they work. You can do it a lot of ways that will
generate a lot of heat, and this method doesn't have that problem. It is
an awful lot easier to just buy a power panel than to do the design and then
collect the parts and put it all together. But then you can learn a lot and
save a few dollars if you do it yourself.
Have fun!
--
Doug Ingraham (Owner/Design Engineer/SysAdmin)
Lofty Pursuits (Makers of fine Electric RC Gadgets since 1992)
loft386!d...@uunet.uu.net
uunet!loft386!dpi