Simplest way to turn on an LED steady from a low PWM signal

Thread Starter

nick9004

Joined Nov 24, 2019
2
Hi, I'm reasonably new to this stuff and in search of some guidance.

I am trying to find a way to turn on a 12V .5A LED from a signal that is PWM. The application is a daytime running light signal on a vehicle. The daytime running light signal is about 13.8V DC and on for approx 4ms off and off for 7ms. I thought about using a transistor to do this but I am worried it will switch too fast and cause the LED to flicker. The LED strip requires an input of 12-15V and draws up to .5A

Any suggestions/comments? Am I right that a transistor will react too fast essentially just creating a different PWM signal?
 

SamR

Joined Mar 19, 2019
2,259
If I remember correctly, anything more than 14 to 16/second is fully on to the eye. Simply convert that to PWM.
 

Audioguru again

Joined Oct 21, 2019
1,593
4ms on then 7ms off is a total of 11ms which switches at 91Hz. Old movies switched at 24Hz and old TVs switched at 60Hz and they both did not flicker. The speed of a switching transistor will not affect the switching frequency.

I guess you are converting old incandescent light bubs in your car to LEDs. It is illegal to tamper with vehicle lights because they might be too bright, too dim, the wrong color or wrong beam width.
 

MrChips

Joined Oct 2, 2009
21,334
UK television used a refresh rate of 25Hz and you can notice flicker.
North American TV (in the past) used 30Hz refresh and you don't see flicker.
 

Thread Starter

nick9004

Joined Nov 24, 2019
2
Thanks for the replies. Sorry I should have phrased this better. The LED strip I’m trying to power up has has a driver module that wants a constant 12v input. More less I’m trying to come up with essentially a relay/transistor that will be turned on by the pwm signal. I’m just unsure how to convert the pwm signal to an analog 12v signal. I understand the rate of flashing being too fast to actually see. Had the LED been fed directly from the PWM this would have been the case but the driver module is the issue.
 
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