My DIY Glow Driver

[averen]

Hey All,
Just wanted to show off my newest creation (still very much in testing!) Anyways, this is my first "real" PIC based design. It's an onboard glow driver, with status LED (3 color) as well as being user programmable. It uses a switch on the transmitter to "arm" the glow plug, but the throttle must also be in the correct range before it will turn on.

Anyways, just wanted to share...total cost was around $8US...right now I'm using a relay for the glow plug, I need to figure out how to get rid of it, but everything else I tried had too high of a resistance and the glow wouldn't get hot enough.

Looks like it pulls 20mA at standby and 60mA when the relay is activated.

This is fun :)

Jared

[gta18]

have you tried pulse width modulation with a mosfet, instead of the relay?

[averen]

I just picked up a mosfet today...haven't tried PWM yet.

Jared

[misplacedtexan]

i am interested in building my own glow driver. can you tell me the parts needed and also,maybe a schematic? where did you obtain the parts? thanks, Alan.

[averen]

The parts are fairly simple:
1 Microchip PIC12F675 Processor
1 NPN transistor (don't have the model number on me now...but they're available at radio shack in a 15 pack for about $3)
1 - 1A 5V Coil Relay (also radio shack)
1 diode
and a couple of resistors...and a 2 color LED.

I still have some testing to do. Once I get everything straightened out and hopefully get rid of the relay I plan on posting a schematic as well as the hex for the chip. I'll probably sell a couple of pre-programed chips as well if anyone is interested that doesn't have a programmer. Right now I'm working on compacting the circuit board and will be etching some of my own. The resistors for the LED can be "inline" with the led wires, which will drop down on the board space. My goal is to make the thing smaller than the Sub-C cell on the board, I think this will be fairly easy to do. I'm also contemplating using a SOIC rather than a DIP, which will cut down on space even more.

I picked up the PICs from Newark, everything else is easily obtainable locally.

Jared

[Gary Warner]

have you tried pulse width modulation with a mosfet, instead of the relay?

If the battery for the glow plug is 1.2 volts, it wouldn't need to use PWM. Just apply a high at the gate and current flows. Use of logic level FET would be best. If using a normal 10 volt gate, you could use a PWM pulse through a voltage doublers to get the 10 volts. A FET with 10 volt gate could be used at 5 volts, though it won't be full saturated in the 'on' state. You might concider using opto coupling (usualy at the signal input) to avoid bringing the driver and radio grounds together (reduce chances of RFI).

[Richard Ingram]

If you want to see how an old version of this was done take a look at this link

http://www.e-radiocontrol.com.ar/vieja/downloads/Optoglo.pdf

The schematic at the end shows how you might integrate a solid state relay.

[averen]

Mine is fairly similar in design, but it's more geared toward being only an onboard glow driver (although it is possibly to use it for a switch, just a more complicated one.)

My design uses 2 inputs rather than a single switch:
1 - Throttle (with pass through to the throttle servo)
2 - Switch

The throttle is used so that you can't hot start the engine by setting the glow on(o.k., you can hot start it if you don't program the throttle range correctly...but assuming you program it correctly you cannot hot start it). The range is user programmable so that you can setup an area of the throttle that will allow the glow driver to be turned on with the switch (works for both normal and reversed throttle servos). If the throttle is outside of this range and the switch is on the glow will not be on. This was put in as a safety device as I really like all my fingers :)

Also if you turn on your receiver with the switch and throttle in the "on" position it will wait to heat the glow plug until you turn the switch off and back on...again, because I like my fingers.

The optoglo design is good (I'm not bashing it at ALL!), but I wanted something with more safety features pretty much only for glow plug use (and I really like reinventing the wheel). I think I will look over the documentation some more and see how the FETs are used rather than the relay.

Jared

[Richard Ingram]

The optoglo design is good (I'm not bashing it at ALL!), but I wanted something with more safety features pretty much only for glow plug use (and I really like reinventing the wheel). I think I will look over the documentation some more and see how the FETs are used rather than the relay.


I agree. The reference to the Optoglo was just to give an example of the solid state relay. I like the 'no hot start' feature, particularly relative to helicopters !!

[averen]

I have some video of the programming that I'll post later today or tomorrow...unfortunately it's quicktime, and uncompressed, so I'll probably have to re-record it or convert it to something that I can edit.

Once I get the circuit boards designed I'll be posting everything here for free (with the exception of the source...but I'll post the hex). I really suck at doing circuit board work, and this is a fairly simple one too!

Jared

[dpbarry]

This site has an opto isolated glow driver. Not sure what the safety features are though.

http://www.emsjomar.com/SearchResult.aspx?CategoryID=6

This other site has one as well which does seem to have safety feature to a certain degree.

http://www.nelsonhobby.com/electr.html

Declan

[Richard Ingram]

One of the neatest products I have seen recently is the Align 2 in 1 regulator / glowdriver. Fot those using a li-poly + regulator you can get a glow driver all in the same package.

[Cameldog]

So its been a while, any chance of seeing those plans? I am very intrested in making my own!!!

Thanks

[gta18]

Pwm works like a charm for this application

[lazy-b]

futaba has such a product call GH-1 that can Drive a Glow Plug using a Receiver Battery pack, it uses a very high efficient DC-DC converter......The Futaba GH-1 draw just about 1 amps when Powering the Glow Plug.

Have installed a Futaba GH-1 on my Scale Helicopter, I make a Micro-SWITCH that automatically turned on the Glow Igniter when a Shaft starter is inserted.

I have tried using a PWM using a simple 555 timer and a power mosfet, you can not directly just tap it in a Receiver due to very high peak current (16 Amps Peak current, average is about 4 AMPS......assuming a PWM Duty Cyle of 25%, need to drop 4.8 Volts to 1.2 Volts), You need to directly tap it on the Receiver Battery.

if you use a High Capacity Nicad Battery, I guess, its more simple just use a Simple Dropping Resistor to drop the voltage from 4.8 Volts to 1.2 Volts by using a 1 Ohms/ 10 Watts resistor........its just a Few Second activation just enough to start the engine.