Finding out the serial number of a trimmer

Thread Starter

Alin Manea

Joined Dec 5, 2017
3
Hello, I just changed all the leds in my car dashboard and I can't seem to notice that they are a little bit brighter than i would like, even on the lowest brightness settings, the circuit that is responsible with the brightness adjustment uses a Infineon BTS730 which has an integrated pwm controller and a 4-5K trimmer made by Piher Spain, but I've been unable to find the model id or anything about it. There is a serial number written on the side but it is unreadable (3541 maybe). I would like to make the new leds dimmer so I am thinking of replacing the current trimmer with a 10 or 15K one, but I need some help into identifying the type I need.
https://i.imgur.com/sk8YTcp.jpg
https://i.imgur.com/vq77knr.jpg
https://i.imgur.com/e1odZA4.jpg
 

wayneh

Joined Sep 9, 2010
16,400
It's possible that changing the resistor will not help you get to a lower duty cycle on the PWM output. The data sheet for that controller says the minimum duty cycle is 14%, and it's likely that the existing pot already allows you to achieve that minimum.

That said, you could experiment by placing a fixed resistor in series with the trimpot. If adding 5K or whatever achieves what you want, then you'll know you're on the right track. But I'm not optimistic.

You might just add a power resistor in series with your LEDs. It's hard to speculate without the details but I imagine 10Ω might give considerable dimming. The resistor will need to be rated to double the LED current, to provide a margin of safety to avoid overheating the resistor.
 

Thread Starter

Alin Manea

Joined Dec 5, 2017
3
It's possible that changing the resistor will not help you get to a lower duty cycle on the PWM output. The data sheet for that controller says the minimum duty cycle is 14%, and it's likely that the existing pot already allows you to achieve that minimum.

That said, you could experiment by placing a fixed resistor in series with the trimpot. If adding 5K or whatever achieves what you want, then you'll know you're on the right track. But I'm not optimistic.

You might just add a power resistor in series with your LEDs. It's hard to speculate without the details but I imagine 10Ω might give considerable dimming. The resistor will need to be rated to double the LED current, to provide a margin of safety to avoid overheating the resistor.
Thank you for your reply, you might be right about the duty cycle. Unfortunately I can't really place a resistor in series with the trimpot without either removing the pot or the ic. Also adding a resistor to the leds isn't doable either, as there are more than 40 leds that would require that. I might have to change the smds with some that are dimmer afterall.
 

RichardO

Joined May 4, 2013
2,271
I might have to change the smds with some that are dimmer afterall.
The Car Guys would recommend black electrical tape. :D

But, seriously, maybe you should consider putting some kind of neutral density filter between you and the LED's. Maybe you could print a fine dot pattern on a sheet of clear Mylar. Visualize halftone printing.
 

Thread Starter

Alin Manea

Joined Dec 5, 2017
3
The Car Guys would recommend black electrical tape. :D

But, seriously, maybe you should consider putting some kind of neutral density filter between you and the LED's. Maybe you could print a fine dot pattern on a sheet of clear Mylar. Visualize halftone printing.
:D This might actually work. I will give it a try before anything else. Thank you.
 
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