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On-Board glow and RX same battery issue

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On-Board glow and RX same battery issue

Old 11-26-2010, 08:52 PM
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ZachB10
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Default On-Board glow and RX same battery issue

I recently switched over to Hobbico LiFe batteries. I have been using an on-board glow system (Sullivan) with a separate receiver and glow ignitor battery for some time with no issue now. However, with the LiFe battery, which has 2 power leads, I would like to run the glow and receiver off the same battery. With a 2100mah LiFe battery on a 60 size ultra stick, there will be no issue running both on the same battery and I can lose some weight.

I hooked up one of my other planes doing the above with no issues at all. Same brand (Sullivan) on board glow.

However, on the stick, it immediately began smoking - not good. It melted the ground wire. I figured I may have a faulty switch (one of the charge leads on the switch was all botched up) so I replaced the power switch, and this time, the switch fried. There's something wrong, I have no idea what, as the receiver powered separately works fine, as well as the glow. Hook them both up to the same LiFe battery and it either fries a switch or melts the ground wire.

Very confused. Ideas? I would prefer not to melt more wires or fry another $12 switch (or fry the glow ignitor).

Thanks in advance!
Old 11-26-2010, 10:38 PM
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jester_s1
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Default RE: On-Board glow and RX same battery issue

You're shorting out somehow if it fries it immediately. Install a new switch and go over the setup with a meter to check for shorts.
Old 11-26-2010, 10:44 PM
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ZachB10
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Default RE: On-Board glow and RX same battery issue

Where would I check for shorts? This is the confusing part.
I have a standard power switch installed between the receiver, and one power lead of the battery, to turn the receiver off and on. Of course, all servos plug in to the receiver - they all operate normally.
I have the Sullivan glow grounded to the engine, and attached to the glow plug. It operates normally when connected to it's own battery.
The throttle servo connects to the glow ignitor, and the glow ignitor then has a lead that plugs into the throttle servo position on the receiver.
All operate as normal until I plug the power into the Sullivan glow power connector.
I unplugged the throttle servo lead that comes from the glow to the receiver and it still did the same. I unplugged the servo itself from the sullivan. Same. I have no idea where or what to check at this point.

I've got to be missing something obvious.
Old 11-27-2010, 01:37 AM
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Rcpilot
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Default RE: On-Board glow and RX same battery issue

Did you plug the glow unit into the RX backwards? Positive + and negative - wires mixed up? It's happened to me before. []
Old 11-27-2010, 02:53 AM
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ZachB10
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Default RE: On-Board glow and RX same battery issue


ORIGINAL: Rcpilot

Did you plug the glow unit into the RX backwards? Positive + and negative - wires mixed up? It's happened to me before. []
Good thought, but no. It was working prior, as it's a standard servo lead that plugs into the receiver and the positive and negative wires were lined up correctly. It even shorted without the lead plugged into the receiver

Old 11-27-2010, 06:48 AM
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Default RE: On-Board glow and RX same battery issue

Check to make sure that the polarity on the glow plug from the on board glow is correct.....I wouldn't run a single battery anyway...if something happens to your on board glow and it drains your battery, you lost an airplane
Old 11-27-2010, 12:33 PM
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Default RE: On-Board glow and RX same battery issue

I am not sure about your glow driver setup but most I have used have the negative connected to the glow plug and the positive connected to the ground, they are opposite of typical electrical systems. You would not notice this with separate batteries, as you have essentially a + voltage, a common and a - voltage, but if you try running it all on the same battery it will not work because you wind up with what is called a ground loop.

Edit to add:
The glow driver ground is positive to it's battery and it's output is negative when using two batteries the interconnect to the rx/servo lead is used as a common and ends up having both the negative of the receiver and the positive of the driver wired together but neither see the other battery connection. trying to power them both on the same battery ties the positive and negative together and there is your short or ground loop.
Bad news is that you may have cooked your glow driver but the RX may have survived...
Old 11-27-2010, 12:59 PM
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Default RE: On-Board glow and RX same battery issue

It works properly on one plane, so I would assume that with the same model battery, receiver, and glow system it should work on another plane. 

How would I go about testing the polarity of the plug?  Sorry, but I'm not all that great with electrical and the sort.  
Old 11-27-2010, 01:09 PM
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Default RE: On-Board glow and RX same battery issue

That is a bit weird...
Have you by chance had to add any shielding or ground to the motor to prevent RFI in this plane?
If not I check to see if you have a wire that is next to a control rod or cable, even another wire that has chaffed and caused a short.
To check what is going on use a ohm meter in place of your battery (be sure to disconnect the battery) and start unplugging things till the short (a low ohm reading on the meter goes away) and this will at least show you were the problem is.

Good luck!
Let us know what you find.
Old 11-27-2010, 01:15 PM
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Tall Paul
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Default RE: On-Board glow and RX same battery issue


ORIGINAL: ZachB10

It works properly on one plane, so I would assume that with the same model battery, receiver, and glow system it should work on another plane.

How would I go about testing the polarity of the plug? Sorry, but I'm not all that great with electrical and the sort.
.
The plug has no polarity.
It is just another wire.
The on-board glow I used had a separate battery and activating switch.
I'd -never- attach anything like that to the receiver battery.
Old 11-27-2010, 01:28 PM
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ZachB10
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Default RE: On-Board glow and RX same battery issue

This one has it's own switch as well. They recommend that you use a separate battery, but since I only activate the glow at 1/4 throttle and under, it's going to remain off most of the time The servos are standard servos so I don't think that the battery will be drained in one or two flights, after which I will check the battery and can charge it back up if necessary in a short period of time.

When I powered up the receiver everything works properly. Looks like the glow still works as well. I'll go through the setup later today and check for shorts with a meter. Hopefully something pops up.
Old 11-27-2010, 01:41 PM
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Default RE: On-Board glow and RX same battery issue

Good luck!

Using a meter will keep you from "cooking" anything until you have it sorted out.
Now both the receiver and glow driver will present a load to your meter I'm not sure what the ohms reading you will see but there will always be some with the power switch turned on, but the short that cook wires and the switch will be very low, essentially very close to zero. Hope this helps...

By the way I am with Tall Paul it's not a good idea "to put all your eggs in one basket" it is much safer to use two battery's if the glow heads south with one battery you could lose control of the plane, with a separate RX battery worst case if the glow driver fails is a dead stick landing.
Old 11-27-2010, 01:49 PM
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ZachB10
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Default RE: On-Board glow and RX same battery issue

Hmm.  Perhaps I should just keep them separate.  My curiosity has me going though, I still want to find why it's doing this.  

Thanks for the explanation, I was wondering why having a second battery hooked up wasn't causing issues.
The glow driver ground is positive to it's battery and it's output is negative when using two batteries the interconnect to the rx/servo lead is used as a common and ends up having both the negative of the receiver and the positive of the driver wired together but neither see the other battery connection. trying to power them both on the same battery ties the positive and negative together and there is your short or ground loop.


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