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Daniel Wee

Receiver getting real hot ... why?

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I've been using the standard receiver as most of you have and noticed that during operation, it gets pretty warm. This is running off a 3S battery. Has anyone opened up the receiver to figure out what's causing the heat? My guess is that the voltage regulator is the one heating up the whole receiver. If so, can we run this thing at a lower voltage and still have it work? Hopefully with less power dissipation. It seems such a waste to let all that power go to heating, not to mention the heat affecting the oscillator and PLL stability. Anyone looked into this before?

Daniel

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That can work, or not. On many RXs the major part of the circuitry is indeed powered in 5V via a regulator, but there's sometimes a small part that draws close to nothing but which requires the full input voltage and thus taps before the regulator. And it's a pain when you accidentally reverse supply voltage as the reg will protect what is behind, but not that directly connected part.... <_<

Just measure the current draw and check if it's realistic, most RXs are in the 200-300mA range.

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why not mention WHAT type of receiver you talk about ?

also see here:

http://www.webx.dk/rc/video-wireless/video.htm

goto halve of the page

also I can mention this receiver gets burning hot

at 12-14Volt supply indoor test, but outdoor tests shown no problems

due to wind cooling really works impressively good.

Edited by ThomasScherrer

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That's exactly the receiver I'm referring to. It is true that with wind blowing, it doesn't get too hot but I'm more concerned about the efficiency that must be occurring in order to be producing that much heat - wasted power which may be better employed.

Daniel

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I was thinking maybe if I use a switching regulator, the heat problem will go away?

Daniel

You risk to introduce interference on the receiver circuit, don't do that. You can lower the input voltage to reduce heat. All receivers that I've seen are rated for 12V but work at 100% on 9.6Vdc, you will see an evident reduction in heat.

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I think I'll give that a try. However, a well-designed switching regulator should not be any different from a linear regulator, especially since the current draw in this application is constant in steady state. I know it doesn't work at 2S voltages so that's a bummer. I'll do some tests once I get some time to see what the actual voltage range is.

Daniel

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For what I suppose those receivers have comtech modules inside which need a certain voltage to operate properly.

If the circuit which the manufacturer designed permits, it might be possible to go as low as ~8V. The standard circuit at the moment requires more than 9V since there is linear reg for 9V output which supplies the audio demodulator IC, as well as a couple of other components. So this might get difficult then.

However, it seems that the comtech modules themselves seem to operate at voltages below 9V, as long as the voltage at the VCO power supply pin is high enough to ensure proper regulation.

Further information can be found here:

http://www.lechner-cctv.com/download.php?F...M2400RTIM8B.pdf

On Page#5 you'll find the pinout of the module, look for Pin11.

http://www.klein-electronic.de/download/DF...400RTIM8-00.pdf

On Page#2 you'll find the default schematic.

I hope this might help a little.

A short word regarding switching reg versus linear regs:

Switching regs have a slower responce to input voltage changes as well as load changes compared to linear regs, and, as VRflyer said, they might emit electrical noise due to their switching which might cause interference with sensitive components as receivers.

However, in the schematic of the standard circuit for the Comtech receiver you can see that they use a switching reg, just give it a try.

The best results I got was the combination of a switching reg in series with a linear reg. The sw-reg gives a suitable voltage to put into the linear reg, just high enough to ensure proper work of the lin-reg. This way the lin-reg doesn't get unnecessaryly hot. The lin-reg actually performs as a kind of "noise-filter" which reduces noise on the power wires.

cheers,

Hartwig

Edited by Hartwig

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That's correct - and my point precisely - the receiver presents a relatively constant load to the regulator so it should not be a problem, unlike say for high intermittent current draws. For stable non-fluctuating loads such as the receiver, all you really need is just a bigger smoothing capacitor. The switching PWM duty cycle and frequency should be relatively constant too. I've ordered one of the Dimension Engineering modules to test this out. I've got a feeling this is going to work out.

Daniel

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Just a little add-on: The switching regs of Dimension Engineering are great from my experience. However if you should have problems with interference, you can try adding a few low capacitance caps as well because the big cap might be too sluggish to compensate the high frequency components of the reg's switching.

I tried the DE-SW-Regs as a BEC and my RC-receiver just refused to work. The "Filtering-method" with the linear reg, which I described before, solved the problem.

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(I degraded an entire summer's flying video in 2003 thanks to using a SMPSU - assumed all the twitchiness in the R/C was to do with the aircraft. Come autumn, tried linear regulation, all the twitching stopped. Argh! I'm sure things can get better with careful layout & suppression, but once bitten, twice shy - I have enough problems trying to get decent video without the camera servos having fits)

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