Hey,

you guys are my last chance... i googled like hell, asked a lot of people but still no luck. And T-Motor isn't available for the next few days because of the chinese holidays.

OK so: i bought the T-Motor F7 Mini Stack: https://uav-en.tmotor.com/html/2020/Flig...6/354.html
I build the copter and everything works fine except the current sensor.
It shows an amp draw of about 30A when it is just sitting there doing nothing. Just the battery connected. The amperemeter scale is set to 200 (recomended from t-motor). In reallity it pulls only about 0,5A. 
It won't change at all if i spin the motors up even with props on. It decreases slightly but i suspect that is because of the voltage sag of the battery what results/calculates in a slightly lower amp draw.


I have absolutely no idea how to solve this.
Here is a quite similar issue but it was a wiring problem: https://github.com/betaflight/betaflight/issues/8315

What i did for troubleshooting:

• checked the wiring from esc to fc (a lot!) i used the provided wiring harnes. There are GND, VBat, Motor 1-4, Current, Telemetry. GND and VBat are OK because the board powers up. Motor wires are OK because all motors are controllable. Telemetry is OK because i get voltage and temp from the esc (sadly no amp draw). So i suspect current must be connected correctly. 
  
• erased the fc and flashed it with different versions and changed nothing but the amperemeter scale. 
  
• i am buliding a second slightly different drone with the same stack == same problem
  
• i have another drone with the bigger T-Motor F7 HD FC and a F55A Pro II ESC and everything works fine. BF targets are the same for the standard T-Motor F7 and the F7 Mini
  

I apreciate any idea you guys have! Thank you.

I think there may have hardware bug with the ESC itself based on your description and the fact you are getting the same issue on two ESC boards. Another member on here has the same issue with one of their 30x30 stacks. Unfortunately T-Motor just replied to them saying that most people don't use the ESC current sensor and not to worry about it, which wasn't a very helpful answer. So don't expect any help form T-Motor because they don't seem to know.

You have to set the current for "onboard ADC". See if that works. There is no current value from the ESC sensor (digital telemetry).

(01-Oct-2020, 03:42 PM)voodoo614 Wrote: You have to set the current for "onboard ADC". See if that works. There is no current value from the ESC sensor (digital telemetry).

Current sensor ist set to onboard ADC. And yes, the ESC doesn't send telemetry values for current. 

Thank you @ SnowLeopardFPV
That's annoying. I thought it would be better to spend a few extra bucks for higher quality fc and esc. At least i thought T-Motor has higher quality standards.

(01-Oct-2020, 03:53 PM)ÄndyRändy Wrote: That's annoying. I thought it would be better to spend a few extra bucks for higher quality fc and esc. At least i thought T-Motor has higher quality standards.

We don't believe that T-Motor make their own ESCs or FCs. They are a motor manufacturing specialist. My understanding is that they outsource the electronics to another manufacturer and just put the T-Motor branding on them, but we don't know who that is. This is probably why they can't answer any technical questions about their branded electronics that aren't already on an FAQ sheet.

(01-Oct-2020, 03:53 PM)ÄndyRändy Wrote: Current sensor ist set to onboard ADC. And yes, the ESC doesn't send telemetry values for current. 

Thank you @ SnowLeopardFPV
That's annoying. I thought it would be better to spend a few extra bucks for higher quality fc and esc. At least i thought T-Motor has higher quality standards.

You are the third person in the last week with problem with ESC telemetry.  That is bad paying all that money for a product to not work.  Can you get a refund from your vendor?

(01-Oct-2020, 04:07 PM)SnowLeopardFPV Wrote: We don't believe that T-Motor make their own ESCs or FCs. They are a motor manufacturing specialist. My understanding is that they outsource the electronics to another manufacturer and just put the T-Motor branding on them, but we don't know who that is. This is probably why they can't answer any technical questions about their branded electronics that aren't already on an FAQ sheet.

I suspected that. But i heard some good things about T-Motor electronics and Drone Mesh did a review on the F55A Pro II which sounded pretty impressive. 
But: lesson learned.
Which brand would you recommend if the electronics should not only perform well but also be reliable and robust without looking at the price tag?
I want to use both of those drones i am building right now for commercial flights. Thats why reliability is important to me.

(01-Oct-2020, 05:11 PM)voodoo614 Wrote: You are the third person in the last week with problem with ESC telemetry.  That is bad paying all that money for a product to not work.  Can you get a refund from your vendor?

I bought those items from unmannedtech. They already know about my problem but want to contact T-Motor first. But right now i would very much apreciate it, if i could just return it.

Same problem here man: https://intofpv.com/t-t-motor-f7-amp-dra...sd-unarmed

You can forward my epic battle against T-Motor braintrust support to Unmannedtech if you like.

(01-Oct-2020, 06:46 PM)the.ronin Wrote: Same problem here man:  https://intofpv.com/t-t-motor-f7-amp-dra...sd-unarmed

You can forward my epic battle against T-Motor braintrust support to Unmannedtech if you like.

Hey thank you! I will forward it to unmannedtech!

I did some further testing:
As i said i have a copter with 30x30 T-Motor F7 FC and a T-Motor F55A Pro II F3 ESC which is working fine. The readings without load seem a bit (showing 3 A instad of 0,7A) off but under load everything is fine and the amp draw seems pretty accurate especially when compared to the used mA/h and charged mA/h.

Long answer short:

• if i connect any ESC to the big T-Motor F7 FC the amp draw reading is ok.
  
• if i connect any ESC to the T-Motor mini F7 FC the amp draw is completely off. (on both F7 mini)
  

It seems the ADC Sensor part of the T-Motor F7 Mini is defective oder somehow not connected. As the.ronin assumed in his thread about the same problem i also asume that the ADC sensor somehow reads phantom voltage which might be induced by nearby electronics.

The reason for my 30x30 T-Motor F7 FC is working and the.ronin's is not might be that i ordered this FC directly from the T-Motor store. It might be that T-Motor (or whoever is manufacturing theses boards) i very well aware of this problem and i got a FC from a newer batch.
The mini F7 i ordered from unmannedtech might be also a older batch like the one from the.ronin and be therfore affected by the same problem. After all the big and the small one share the same BF Target and as it seems at least 95% of the same electronics.

Thanks for the research, Andy.

Hmmm ... so in my case, we were thinking it was the current reading coming from the ESC that was off. I thought this meant the current sensor was on the ESC. If the ADC sensor is on the FC, what is the thing called on the ESC that is sending data over the current wire to the FC? Sorry I'm a little confused.

I concur with your theory about T-Motor sending you a "quietly fixed" FC. I would not put it past any of these bastards to quietly bury a defect to save a few bucks despite charging a premium.

Current sensor is on the ESC. The sensor circuit takes the amp draw and outputs a proportional voltage on the current wire. The FC ADC reads the voltage (0-3.3V) that the current wire provides. Along with the offset and scaling settings, you adjust to calibrate the current in BFC.

With the help from unmannedtech it seems T-Motor is acknowledging that there is in fact a problem with the FC. They agreed to sending me replacement flight controllers.
Fingers crossed.

Ronin, maybe you can get onboard. No pun intended.