Trying to dim a set of LED lit Autometer car gauges. The O2 gauge has no access to the low side so the N mosfet I had working on the rest of the gauges does not work on the O2 gauges. I have tried the attached circuit but it does not seem to work correctly. Is there a board available to control LED brightness from the high + side?
it does not seem to work correctly.
If you want help on this forum, you will have to explain things more accurately than that. We are not psychics.
Why that MOSFET? It can switch 47A @ 60V. Do you really need something like that to switch an illumination led? What MOSFET are you using for the other gauges, and are you using one MOSFET for many gauges or one for each?
The high side driver I posted was the only one I could find that I had the parts for right off the bat. I was hoping someone on here would have already done something similar that they had a circuit for or possibly there was a shield available already.
I started with a low side dimmer using an N mosfet that worked really well until I realized there was no access to the low side for the O2 gauge.
There are 6 gauges total. Draw is approx 205mA to light the gauges. The only way to dim these 12v gauges is PWM on the high side. Is there a simple circuit I could build to control these gauges?
Does it work as in the diagram?
i.e. by simply applying 5v to the "pin 5v" .(and ground naturally)
Oh for pete's sake, circuit works fine, the 2N3904, brand new, was toast. Should have known always check the simple things first.
Thank you BlueJets for the suggestion to check with 0v and 5v direct. soon as that didn't change anything I knew the trans was toast.
Maybe someone else can use this circuit for dimming LED's on the high side. What kind of max current could this circuit control? I have an RV that I was going to Arduino as well and it has a bunch of 12v puck lights that could use a dimmer!
Thank you all for your reply's!
Slider69:
What kind of max current could this circuit control?
See post #1. Of course if you put even half that maximum current through it, you should add a heatsink.
For 250mA, that MOSFET is way overkill. An ordinary pnp transistor like bc327 will be adequate.