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HelicopterMain Discussion › electrician guru's please stand up
11-26-2007 01:05 PM  10 years agoPost 1
krashtagain

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ohio

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ok guys , who has the prints for building your own stepdown for an onboard glow starter . yes i know there are some you can buy but i'm looking for prints to build my own .

If you're not living on the edge you're just taking up space !

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11-26-2007 04:35 PM  10 years agoPost 2
stickyfox

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Rochester, NY - US

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What are you trying to do, run a glow plug from a RX or larger battery? It's easy enough to do in a number of ways.

I would personally use an LM317 regulator configured as a current driver; that way you know you're getting the same heat every time. Unfortunately I don't know off the top of my head how much current that is. I will give it a shot next time I have a glow plug handy and let you know what I find.

Total cost would be about $4 if you had to go to RS for the parts.

-fox

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11-26-2007 05:43 PM  10 years agoPost 3
wlfk

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uk

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How much current does it take to make a glowplug glow? And what voltage do they work at?

K

A bit like a kite, but 500 times more expensive

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11-26-2007 05:47 PM  10 years agoPost 4
Andy from Sandy

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They work on 1.5 or 2 volts at 4 to 5 amps.

The glow driver in a flight panel uses a pulsing system that if measured off load with a voltmeter will actually show as 12 volts.

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11-26-2007 05:55 PM  10 years agoPost 5
AirWolfRC

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A typical glow plug runs at 2.5 to 3.0 amps from a 1.2 to 1.5 volt source.

If you use an LM317, a linear regulator, you will need 2.5 to 3.0 amps from your battery . . . . NOT GOOD.

If you use a switching regulator with about 75% efficiency, you can expect to pull about 0.8 to 1.2 amps from your 5 volt pack.

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11-26-2007 06:03 PM  10 years agoPost 6
spog

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Ontario, Canada

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Switching regulator for sure, configured as a voltage regulator, not a current regulator. That way the glow plug will get more current when doused with fuel(flooded engine). An LM317 won't do it, it's current limited at about 1.5 amps. Use an LM338 if you want to go the linear route.
A google search will find several good circuits.

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11-26-2007 08:10 PM  10 years agoPost 7
stickyfox

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Good point about the fuel. You might want the thing to draw more amps when it's wet.

However, I disagree about using switching regulators. They will almost certainly reduce the sensitivity of your receiver due to the RF noise they generate. I'm sure it's been done, but you are planning on attaching this circuit to your receiver pack right? I'd stick with a linear design.

A big heli can easily draw 2-3 amps from just the servos in an aggressive maneuver. How long do we want this thing to operate at a time?

While you're at it, why not put a small Lipo on board to power the thing? It will solve both problems.

-fox

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11-26-2007 09:13 PM  10 years agoPost 8
wlfk

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uk

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Even if you use a voltage source, do you need some current limiting in there too? Lightbulbs draw a high current when you start them, because they have low resistance until they've heated up. This means that they're most likely to be damaged when you flip the switch and large currents flow.

I don't know anything about glowplugs, but I thought you only needed to run them when starting up? So current consumption isn't a huge issue. Unless it takes ages to start up.

I don't see any value of a linear regulator over a large resistor. A regulator for your radio is important because when you change the volume, the current draw changes. Your glowplug will have a fixed resistance, unless perhaps you change to a different type of plug.

I can imagine all kinds of clever circuitry to control this. Perhaps you press a button and the glow-plug is fired for 10 seconds. Or perhaps it cleverly senses a change in glow-plug resistance (related to temperature) and only turns off when it knows the engine is running...

K

A bit like a kite, but 500 times more expensive

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11-27-2007 09:05 AM  10 years agoPost 9
ChristianM

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Oslo, Norway

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They will almost certainly reduce the sensitivity of your receiver due to the RF noise they generate
I agree that that can be an issue if it is not shielded properly but really it is a non-issue since you start the engine, turn off the glow igniter and then fly. It does not generate noise when it is off.

Christian

Burn fuel, be happy

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11-27-2007 10:33 AM  10 years agoPost 10
mdu6

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Montreal

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11-27-2007 11:46 AM  10 years agoPost 11
Hamo

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Ireland

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11-27-2007 01:57 PM  10 years agoPost 12
krashtagain

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ohio

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very good info guys , thanx alot

If you're not living on the edge you're just taking up space !

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11-27-2007 03:59 PM  10 years agoPost 13
AirWolfRC

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The first circuit using LM555 timers is interesting but prone to making interference.

That circuit using the TL494 is the better one because it is, in fact, a switching step down voltage regulator circuit that includes an inductor and diode in the output. That prevents high current square waves and the consequent interference . . . . and could be added to the LM555 circuit.

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