Help with dead Rc rx

Other Hardware General Electronics
1

Hi guys,
I have posted this over at rcgroups, but it hasnt got much of a response,

I would like to know if anyone can help me out,

Basically I have a 5V regulator , which appears to glitch under heavy load and spike things, It has now spiked three of my four Radio control receiver modules, and Im getting angry. needless to say , the regulator is on its way to the bin and will not be used with my fourth module,

Yesterday I hooked up a multimeter in series in order to check the amperage being used, and it was only maxing one amp, the regulator should handle 2.5.
I also hooked in series to check voltages during operation, and could only see it drop by 0.3v during this 1A consumption.

I have had a closer look at the boards overnight,
they have
http://www.avantcom.com.tw/AVANTCOM/...SOLVE/18_3.pdf (one of these)
FT24C02A-5LG-T datasheet - The FT24C02A is 2048 bits of serial Electrical Erasable and Programmable Read Only Memory, commonly known as EEPROM. | FT24C02A-5LG-T.pdf by List of Unclassifed Manufacturers | FT24C02A-5LG-T documentation view on KAZUS.RU ( I assume it has this eeprom, the chip says, FT24CO2A 2MF0MC)
and it has a 3v regulator

Basically, after glitching during a bench test, two of the faulty boards are no longer able to bind with the transmitter, and the other faulty one has a fried voltage regulator,

I have just swapped the voltage regulator on the completely dead board and it now shows signs of life, IE the led flashes to indicate that it is looking for a BIND, but it never gets one, this behavior is the same on all three boards that have been abused.

I have confirmed that the 2.4ghz chip has voltage on pin 19 from the external regulator, and pin 20 is supplying pin 10.
Can anyone suggest a way of checking if the eeprom and 2.4ghz chips are dead or alive?

there is a pic of the board here:

thanks in advance for any help possible

2

It is very unusual for a regulator to generate spikes. However it could be oscillating if there is not enough decoupling on it.
While regulators can handle higher currents it would be unusual for them to work without a heatsink. Is it getting hot? Most regulators have thermal cutouts, maybe thus is tripping.
What is the input voltage?

3

Hi ,
the setup is the following,
3s LIPO battery into one of these :
http://www.ebay.co.uk/itm/Red-LM2596-DC-Buck-Step-Down-Voltage-Adjustable-Converter-Power-Module-Regulator-/291054073365?clk_rvr_id=630997706073
(not exactly that , but near as dammit)
I have that set to 5.5v and power goes directly from it to the Rc Rx, which has a 5V rail and a ground rail, these rails go directly to the servos power.

The onboard voltage regulator for the Rx measures 5.5v on the input (what i suppose is the input) and the output varies between them, the three modules with working regulators measure 4.5, 4.5, 3.5
(Curiously, the lights on the modules with 4.5v blink faster than the 3.5v module)

I have traced the output of the onboard regulator back to the chip on its input pin, and the voltage doesnt change, so all looks ok.
I guess something else on the board was damaged.

4

no heat ,
sorry i missed that ,

5

From the photo on the RC forum its clearly too small a regulator to carry 2.5A - perhaps 0.3A
is all you should expect - those small SMT packages have similar small heat dissipation ratings.

If you need to draw more current provide an external heatsinked TO220 regulator with known
specs.

6

you mean the regulator that is in the ebay listing or the photo of the onboard regulator ?

7

From the photo on the RC forum

Well I can't see anything from the links on the first post. Just a page of Chinese characters for the first, and just Russian text for the other two.

You did not say it was a switching regulator in the first post. In my first reply my comments apply to a linear regulator.

If it is like the eBay ling then it looks a bit amateurish, it looks like someone has just laid out a data sheet circuit with insufficient testing. Switching regulator PCB layout is very hard to do properly. So it is likely that you can get high voltage spikes through one of those.
Have you measured these on an oscilloscope? It is the only way to tell. I would put a pi circuit on the end to add extra decoupling and spike protection.
It is the last circuit on this page:-
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

8

Mike,
the first one also opens chinease crap when i use another pc, but the second one opens a pdf a little lower on the page which is in english , can you not see that either ?

I have since read about my "ebay regulator" that it isnt meant to power servos, I dont know why the hell anyone would sell it in the Rc hobby world without it being able to do that, but hey ho , I guess its because the servos draw too much power and causes it to spike and burn things,
I have lost 3 rc receivers to the piece of $%&t. I am probly going to just conenct it to the mains and enjoy watching it burn. If it cant handle ameprage then the size isnt justified in the model, but thats another story for another day.

I have a few of these ptn78000 which I might rig up instead,

thanks for the link on decoupling, I will have a read , maybe even try to use it , but i dont want to fry another 15 quid receiver by risking the previously mentioned piece of crap.

Back to the other question though , does anyone know of a way I can check out the status of the boards that dont bind and possibly fix them ? I have thought about taking the eeprom off of the good working one and putting on a duff one to see if that way it can bind again, does that sound like an easy way to fry the eeprom on the last working board or like a valid attempt of finding what has died ?

9

Poor soldering - bridging here? --->

10

brilliant vision,
that is a stock photo though ,

11

I have that set to 5.5v and power goes directly from it to the Rc Rx, which has a 5V rail and a ground rail, these rails go directly to the servos power.

Many IC's have a 5.5V max Vcc power specification. The servos motors, if they have suppression diodes, will clamp the spikes to around 6.2V. The more motors running and the higher the speed, the more 6.2V "spikes" there could be. Its best to set the supply to 4.5-5V. Better yet, separate power sources for the electronics and servo motors would be an improvement.

12

So are you suggesting that the servos themselves cause a spike when working ?
that would certainly suggest why it happens when all channels are working and not when only one is working,
also, the Rx only dies when powered from the red 2.5a regulator, if powered from the BEC on the ESC then everything browns out but doesnt get fried,

13

So are you suggesting that the servos themselves cause a spike when working ?

Yes.

I haven't used this hardware before, but from experience with switching relays, solenoids and transformers ... its better to have a separate power source from the electronics. Even if they share a common ground, its better to have separate 5V rails (one for the electronics, one for the motors). The motors don't need accurate voltage regulation, so this gives more alternatives for power sources.

EDIT: If its just not feasible to have separate power supplies, then I would set the existing supply quite low (even as low as 4V) prior to testing. Some extra capacitance on the 5V rail may help.

Does the hardware/documentation show information using separate power connections?

14

Well previous to upgrsding the servos to more powerful ones I had some caps on the 5v rail to help with power demands. After testing they seemed unecesary and I removed them. Maybe a bad move.

The burning of the rx only hapened once I used a seperate power source, but maybe that was the cause in itself, luckily my 5v power to my video cam is seperate and that isnt damaged. Im powering that with the ti module mentioned above. I will get two more and power the servos with them and try not to burn more modules.

Id like to have a go at fixing them still though. I cant work out why allmfour pins on the right side of the eeprom are all connected to ground.

15

Id like to have a go at fixing them still though. I cant work out why allmfour pins on the right side of the eeprom are all connected to ground.

There's ground and 3 address pins on one side. So it looks like the address is hard coded to 000.
http://www.fremontmicrousa.com/pdf/EN-24C02A-300-V1P0.pdf

16

Is the adress where data is stored?

Would this be a good option for powering the servos?

17

Is the adress where data is stored?

No, the address just selects the chip (up to 8 chips/devices can be selected).

Would this be a good option for powering the servos?
Tienda Micro:bit Arduino y Robotica Electan, Maqueen Makey Makey y Mucho Mas

Sorry, I have no experience with these nor the specific motors that you're controlling.
EDIT: It would be good to know the max load current rating for each servo motor.

18

Under normal conditions each servo uses 450ma, under max load upto 1A. There are currently 4 in total. Its very unlikely that I will fly the plane in a way that maxes all four at once. Three could be used hard at once, but by no means would they be maxed. Max is when I hold the servo arm so it cant move, then move it the wrong way a little, that will never happen unless there has been a crash

19

Buck/Boost type voltage regulators are designed for battery applications:

You may need several 5V/2A or four smaller 5V/1A type (1 for each motor).
*** They have a forum where you could ask for the best suited for your application.

20

So are all buck types out of the question? Or would I need to massivly overdo the amps available?