Car side-mirror dimmer simulator circuit - DIY

Thread Starter

fe7565

Joined Aug 13, 2016
15
Would like to make a simple car side-mirror simulator circuit. The side mirrors I installed (for better blind spot) do not have a dimmer circuit and I am getting LIN bus errors since the dimmer wires are disconnected. Would like to DIY something that fools the car into thinking it is connected. Needs to be small, not much bigger than a coin or bottle cap.

Only need to DIY the area with the red circle.

Not sure what the values are in the reference design example:

- Seems R1 is 3.9 Ohm (watts?)
- Seems R2 is 3.3 Ohms (watts?)
- C1 is 2.1F??? (assuming 16V to 50V)

What I was able to research is that I need something that is:

- Max current 400mA
- Operating current 150mA
- Voltage max 1.4V, although reference design shows 12V going to it
- About 1F in capacitance
- has shunt resistors
- the actual mirror with dimmer reads 100 Ohm when discharged


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Here is a design reference example:

Texas Instruments Automotive Auto-dimming Mirror Driver Reference Design

PS: the best way would be to send LIN messages that says the dimer is there, but do not have the time to dive deep into deciphering/isolating LIN messages
 
Last edited:

Thread Starter

fe7565

Joined Aug 13, 2016
15
I copied the circuit from the linked TI reference design. I am sure C2 is not 1T. But I only need to recreate the dimming-mirror values marked by the red circle. And trying to figure C1 's value of 21? or 2.1? Also would be good to know the R1 and R2 resistor power ratings. Although the OEM dimming-mirror only draws up to 400mA.
 

Thread Starter

fe7565

Joined Aug 13, 2016
15
Measured the OEM mirror with dimming with a cheap Chinese capacitor measurement device. This is what I got for the OEM dimming mirror: 57.47 mF, ESR= 39 Ohm, Vloss= 30%
 
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