Electronics Chaser LED's, resisters and all things in between

ok, i now have a VU meter that used the lm3915 chip. 2 chips are used for left and right. Now which transister do i use with this one? The PNP or NPN? I need to know this before i hook it up, i do not want to blow it up like i did with the last thing i tryed using a PNP......

Thanks,
David

 

Need manufacture/part number of VU meter please.

 

Its a EB206AD NATIONAL SIMICONDUCTOR

LM3915n-1

Thanks,
David

 

Well, not what I had in mind. I meant a general purpose multimeter to measure the voltage coming off your outputs of the Varad board.

The LM3915n is a decible bargraph display driver. You would need to knoiw your output voltage beforehand to calculate your reference voltage for wiring it up, a whole nother project.

OK. Ive read the posts. The NPN (wired with E and C both ways) does not work at all. The PNP turns it on, but doesnt flash. So your ouput normally stays low, and probably goes high to turn on the LED originally connected to the board. The NPN should work, unless the output just does not go high enough to drive the NPN.

You really need a multimeter. The problem is that you removed just the LED from the board. This means that the circuit had to have resistors in there to limit the LED current, and are still active in the circuit. The Varad chip may have them built inside. We have no idea what voltage swing is used to drive the LED. If you take the leads off of a multimeter and measure the voltage across the output of the Varad circuit and ground, you should be able to see what the voltage output is so we can determine if this is active low or high. From there, we could give you a diagram as to which transistor to use, and how to wire it up.