Automotive clock brightness

Thread Starter

RAN555

Joined Sep 23, 2015
2
Hi,

I have bought a automotive clock and would like to have a potentiometer to regulate the display intensity. Is there any way to do this?
Display is a 3491BGG 16 Pins, chip is a N76E003AT20
Thank you in advance for your help.

Clock.png
Clock_1.png
 
Last edited:

Dodgydave

Joined Jun 22, 2012
10,088
You won't be able to do that, the display will be Multiplexed , so the brightness is set by the speed of the refresh rate, .
 

MisterBill2

Joined Jan 23, 2018
9,851
Actually, there is a way to do that, the brightness may be affected by the refresh rate, or not. To some extent the clock/thermometer brightness will vary with supply voltage, and so if you drop the supply voltage a bit it will dim the display some, while at some point the lower voltage will affect the operation.
Most auto clocks also include a dimming function when the headlights are switched on, that terminal may be acessable if it is present. It may not be identified.
 

DickCappels

Joined Aug 21, 2008
7,985
I see four surface mount resistors on the board, very close to the big IC (relatively speaking). I'll bet a whole dollar that one or more of those controls display brightness. If it were my clock and I did not have too much invested in it I would try holding a 1k resistor across each of those and see what effects if any it has in various locations.
 

MisterBill2

Joined Jan 23, 2018
9,851
I see that there is also a battery on the board, obviously to keep tyhe clock running while the car is switched off, since the display appears to be LED, not liquid crystal. That means that the display is powered, probably through that big three terminal device near the power connector. So do a bit of analysis with a high impedance voltmeter and see if there might be an adjustable regulator involved.
 
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