Modifying IKEA Tradfri Sensor (E1525) timeout help wanted

[bob21]

Voltages:

All 3 potmeter legs to MCU (blue): 2.9V - Does not change when potmeter moved
All 3 potmeter legs to MCU (red): ~0.2mV-0.3mV - Does not change when potmeter moved

Resistance:

Top green on potmeter to MCU (red): 67K (turning dial does not change)
Bottom green dot on potmeter to MCU (red): 67K at max time, 110K at minimum time
Unmarked leg to MCU (red): 110K and does not change when potmeter moved

[electrik]

It's confusing me.
The potmeter has three legs. One is positive supply (VDD probably), one is ground and the other one should change voltage of you move the dial. You should measure between ground and the point you want to measure.

Edit
Now you should find out where this third leg is going to

[bob21]

Yeah sorry about that. My inexperience is probably exacerbating things :grimacing: thank you for putting up with me ;)

I am looking at the potmeter, and I think I can fairly say the legs are like this: https://imgur.com/a/1bTBnUo

So with one probe on the variable leg, where to I test with the other probe?

It looks like the variable leg first goes to TP5_1, then to TP5_2, then to the MCU, but it is not clear which pin: https://imgur.com/a/hbgOOBU

[electrik]

@bob21 said in Modifying IKEA Tradfri Sensor (E1525) timeout help wanted:

So with one probe on the variable leg, where to I test with the other probe?

Always to ground

@bob21 said in Modifying IKEA Tradfri Sensor (E1525) timeout help wanted:

It looks like the variable leg first goes to TP5_1, then to TP5_2, then to the MCU, but it is not clear which pin: https://imgur.com/a/hbgOOBU

With the continuity function of your multimeter (when it beeps if you short the probes) you can trace where it goes to.

[bob21]

My meter doesn't beep, but I get a reading of 0.1 between TP5_2 and the second pin from the right, this seems to be the lowest reading by far: https://imgur.com/a/RLFyOBP is this a sign that it is connected here?

But, when I set the potmeter to minimum the Voltage = 2.95, and this doesn't change... the potmeter set to max is still 2.95V... :disappointed:

[electrik]

So, do you measure a voltage change on any of the pins of the potmeter when you change it?
And what is the type of the MCU?

[bob21]

According to the pics I found, the MCU is a Silicon Labs Mighty Gecko EFR32MG1P132GI.

With 1 probe to ground I tested:

Pos leg with dial at 1 minute (min): 2.97V
Pos leg with dial at 15 mins (max): 2.97V
Neg leg with dial at 1 minute (min): 2.96V
Neg leg with dial at 15 mins (max): 2.95V
Variable leg with dial at 1 minute (min): 2.96V
Variable leg with dial at 15 mins (max): 2.97V

Seems like a very small change.. is this enough of a change to be useful?

[electrik]

I'm out of ideas, I'm giving up.
You could try to tie the variable pin to ground but it could damage your sensor

[bob21]

Ok, no worries. I'd like to thank you for spending your time on this :)

[peter_s]

Hello everyone!

Based on the quite useful reverse engineered schematic at https://hackaday.io/project/174308-tradfri-pir-motion-sensor-hacking the measurements were somewhat sabotaged by the 2N7002 (see Connors comment "enables voltage dividers only when triggered").
the transistor is controlled by the Elmos E931.96 PIR motion controller IC.
The latter is programmable by the IKEA TRÅDFRI ICC-1 module's EFR32MG1P132F256GM32 MCU.
E.g.

2. Blind Time 
Ignores motion after the interrupt output is switched back to 0 
Range: 0.5s... 8s. 
The blind time is [Register Value] *0.5s 
 
3. Programmable pulse counter 
1... 4 pulses with sign change in between 
Amount of pulses = [Register Value] + 1 
 
4. Window time 
For noisy environments 
2s... 8s window 
Window time = [Register Value] * 2s + 2s

https://github.com/basilfx/TRADFRI-Hacking gives a good overview on that.

What is the issue with tose 60s?