dbtoutfit

Hi,

I need to have one switch turn on power to my airplane (rc) reciever and also turn on a 1.2v battery for my engines glow plug. I'm guessing I could hook everything up but I need to keep the 1.2v battery from feeding into the 6v pack and visa versa. Some diodes?

Thanks for any help

Pommie

What you need is a double pole double throw (google dpdt) switch. These are effectively two switches in one package. What I don't understand is that normally you would switch the receiver on permanently but the glow plug would only be powered until the engine is started.

Mike.

rjvh

unless it's timed

dbtoutfit

Man I totally forgot about a dpdt switch I have a few brand new ones I can use.

As far as the glow plug. I am running a 4 stroke engine. To make matters worse it's inverted and it's in my brand new Yak 3D.

I plan to run the glow plug hot at all times. Four strokes have a tendency to die out on low idle and/or on throttle blips no matter how well you adjust the low end or high end needle. I fly 3D and this plane is for competition. Flying
3D, like hovering, requires a lot of throttle input and 1-12 inches from the ground in a hover is not a good place to lose your engine. 4 strokes always have a problem keeping heat in the head compared to a 2 stroke thus why they make deeper glow plugs with a heat bar.

I do have a few 1.2 volt C cell Nicads I could use but due to weight I would rather use a lipo battery. I need 1.2v to heat the glow plug. My lipo I have on hand for this job is 3.6v. Any way to bring this down to 1.2v without burning the other 2.4v to waste?

jpanhalt

Why not use something like this: http://sonictronics.com/xcart/home.php?cat=310

I have also seen something that senses the resistance of the glow plug and applies heat as needed, but I can't find the exact source right now. Continuous draw may take a pretty good size battery to last a whole flight, and using a linear regulator on a LiPo just throws away the excess energy as heat. John

dbtoutfit

1500mah 1.2v c cell should be fine. I may just add a micro servo to a switch for the on board glow plug and turn it off or on with my transmitter.

The time I need it most is at start up and while hovering or other similar tricks.

So the Lipo is a no go since I will have to burn the remaining voltage? Suck you can just bottle neck the voltage down with out throwing away the rest to heat.

jpanhalt

A switching regulator essentially does that, but some people have had radio problems with them, and I am not aware of one that makes 1.2 V for the plug. I use a Castle Creations switcher (Castle BEC) in a large electric. You might call their tech service and see what they say. John

dbtoutfit

Sounds like an option.

I am running digital and not analog system so interference should be 0%.

audioguru

Years ago, my 2-stroke airplane engines stopped when the glow plug's battery was disconnected. The engine was at a high RPM not just idling. It turned out to be caused by a new fuel that didn't have enough nitro in it.

Maybe you can spice up your fuel instead of carrying a battery.

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dbtoutfit

Thanks for the advice.

I use high quality fuel. This issue is typical of 4 strokes, especially one mounted inverted..

The engine run great and if it was a typical plane I wouldn't give it a second thought but seeing as I will be flying 3D one little blip or worse the engine dies while I'm in a hover a few inches from the ground its going to smack the ground.

Thanks for all your help.

Hero999

You could make your own switching regulator of course.
http://www.romanblack.com/smps/smps.htm
You'd need to adapt the circuit for the lower voltage though.

Why not just save yourself the bother and use a 2600mAh NiMH cell?

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dbtoutfit

Yea, I had thought of that. I have a few battery packs rated at 2200mAh AA cells.

I could run 2 or 3 in parallel and bump the 2200 to 4400 or 6600.

Just run a bar across all the tops (+) and then a bar across all the bottoms
(-) right?
keeps it at 1.2 volts and adds the mAh rating per cell, times each battery. Is this correct?

Hero999

Paralleling battery banks can cause problems if they aren't all charged equally.


You can buy 2600mHA AA cells; you only need one for your glow plug.

__________________
What's so bad about Microsoft?

Get Opera it's simply a superb browser.