ET5410 rotary encoder issue (fixed) + thermal imaging photos

[andyB2022]

Hi! It's my very first time posting here so sorry if I do some kind of mistake.
I've got on of these ET5410 Electronic Load from banggood. The only issue with it is that the knob on the front with the encoder only increments the value on the display. No matter how I rotate the knob it just increments it. Menus are suffering from the same problem too..

https://youtu.be/htFG2En_Wv0

Up there is a link to better understand this issue. Thank you for your time!

[electr_peter]

Device is defective, rotary encoder doesn't work properly. I suggest to get in touch with the seller for return/repair.
Either rotary encoder or associated circuitry are defective - maybe just a bad solder joint somewhere. Probably easy repair with disassembly and measurement. Do not repair yourself until you get in touch with the seller.

[andyB2022]

Update: Luckily for me it was quite a simple fix (solder bridge across two terminals of the encoder). Photos speek from themselves. Wish this post will help other buyers in case they have the same issue.

I have also took some pics with an IR camera to see how the unit performs at full load. Maximum temp I could measure was 90 degrees Celsius on the rear top Mosfet. It makes sens why the rear ones are hotter then the first one. (as the air goes from intake to exhaust it gets warmer, so the first mosfet sees a lower temperature, it increases the heat of the air and this repeats until the air is finally exhausted.)

I've placed black electrical tape to insulate the screws from the metal painted case as the heatsinks are tied to the positive input of the load, so a short circuit can happen if you bend the case.

Rerouting the transformer cable it's a good ideea too, they have placed it against the radiator and the metal painted case which is not smart. The cable is long enough to get it in between the two thick blue and red cables and back on top of the pcb connector. Avoiding any melting issues.

A must to do thing would be to take out all 6 Mosfets and replace the thermal compound as it is poor quality and in very low amounts.

What I would also do is to replace the fan with a much higher RPM one (this should be done if you will leave the unit at 400W for hours)

A strange thing that caught my attention was that the bottom mosfets are at least 15 degrees cooler than the top ones. This can also be seen (IR photos) by the electrical tape at the exhaust. (notice the change in color and the 2 different temperatures in the pictures)

Encoder solder issue


Fixed


Main pcb


Display Ribbon Cable


Electric tape isolation IR camera sensing


Electric tape isolation IR camera sensing 2


Intake temperature


Intake temperature2


Exhaust temperature


The other side


Bottom radiator cooler than the top one


Mosfets at 400W


Iron core transformer gets pretty warm, around 40 Celsius


Temperature comparison for the IR camera

[electr_peter]

  you solved issue with the encoder. Have you had a chance to look at encoder debouncing as well? Encoder input is slow and sometimes reverse direction - all signs of debouncing issues.
Also, how do you like user interface? IMO it is a bit disappointing due slow response and unnecessary small font size (east-tester-et5411-cheap-programmable-dc-electronic-load)

Rerouting the transformer cable it's a good ideea too, they have placed it against the radiator and the metal painted case which is not smart. The cable is long enough to get it in between the two thick blue and red cables and back on top of the pcb connector. Avoiding any melting issues.

Are you talking about the area noted in red? There is a gap in PCB to allow wires to path through, but it has sharp corners/edges and may cut wires.

[andyB2022]

I'm sorry for late response. I didn't check my email.

Transformer cable routing. You can see the zip tie.


I've noticed the encoder issues too but when we talk about the price of the unit ....we can't have them all. So far I really like it. The encoder goes in reverse direction for me too when I spin it too fast (lack of velocity in the code...).

[CapLeaker]

I've got the same darn problem with the encoder, even put a new one in and that didn't help at all. Mine was so bad, it was barely usable. I mean it took me minutes to change the voltage. Going from lets say 3.3V to 13.8V on the display was torture. So I unplugged the ribbon cable from the USB port on the back at the front panel. That made mine work better. I still toy with the idea replacing mine with one from Uni-T. It looks very similar to the ET5410. Right now I have mine on the bench apart to see if I can find something.

[andyB2022]

Mine has some issues with the USB cable too. If it gets in a strange position the load will display "COMM FAILUARE". Make sure the connector is properly seeded in the header on the PCB.

[CapLeaker]

I took the ribbon cable out. Mine is totally nuts with it plugged in. I tried a few things today like hooking up the USB to something, taking the RS232 chip off the board and adding more bypass caps to the output of that digital pot. Hooking anything up to the USB did absolutely squat. Taking the RS232 chip off, didn't make any improvements like I got with taking the ribbon cable for the USB on the back off. Matter effect it made the rotary encoder go backwards in direction. So I put that chip back. Then I added more bypass caps (0.1uF) to the encoder and that didn't make much of a difference either. No dice today. Maybe I try tomorrow the oscilloscope on it and see if I can see something. Maybe there is noise getting into the line somehow?

[andyB2022]

Have you tried to get in touch with the seller? I've got 50$ refund for my unit.

[CapLeaker]

Yeah, I got a little bit of refund too. However I’d like to fix it.
So I pocked around on this thing with my oscilloscope and DMM. Here’s what I got:

The square wave on the encoder is actually pretty darn good. Didn’t find any bouncing. I did notice that the digital ground from the front face isn’t grounded to earth ground on the chassis. Connecting DGND to earth GND made it slightly better. I am not sure why DGND is floating around. Adding 0.1uF to both sides of the digital encoder to DGND a made it better when I didn’t use the plastic knob. But with that knob on rendered it almost useless again. So this problem hasn’t anything much to do with denouncing the encoder itself. So I looked at the power at the pull up resistors for the encoder. But here I didn’t find anything crazy either, besides the voltage being kind of low for my liking. I got anout 2.9V at either side of the encoder legs. I would have thought there should be something more like 5V there, but maybe I am wrong with that assumption.

[CapLeaker]

Worth mentioning that the main ground going from the plug to the transformer on the bottom was o.k... I did find that the ground from the transformer to the top plate was higher in resistance. A quick loosening and tightening of the screw on the bottom at the transformer fixed that. Since I didn't have anything better to do I swapped out the rotary encoder again and connected the DGND to GND. At the end of the day I still have kinda the same result.  It's usable, but not working as it should. Aarrrgh!