Transistor issues??

[jknightandkarr]

Working with PN2907 & 2N3906 PNP transistors, See link here for information about the project details, https://zappbots.altervista.org/forum/viewtopic.php?f=5&t=318, but I have 5V dc on the Emitters, Collector connected to appropriate value resistors to my leds, 6 in parallel, then out to ground. Moving Base pins to 5V dc and ground to test transistor circuits. Not sure if I damaged them accidentally, they work so idk, but I have 3 transistors when I connected base to ground, the transistor is staying on even if I put the Base at 5V. Smell that lovely burned elect smell, but still work. Need to dig out my cheap tester to check them using it's function. I measured my LED segment, expected 150 mA @ 2.3 V dc, getting 78.8 mA @ 2.3 V, going to test them all to see what each segment draws, but is there possibility that they was damaged, when connected backwards? Should base pin have a resistor?

Joe

Edit: There is a image of a schematic of a display using LM3914, the only diff, besides resistor values is mine, have the load on the Collector, while the diagram has the load before the Emitter.

[jknightandkarr]

Ok...... VERY ODD update...
I have 2 DMM from the EEVBlog's store,
https://www.eevblog.com/product/bm235/
https://www.eevblog.com/product/eevblog-bm786-multimeter/
Now, both meters seam ok, my BM235 I tried to get mA reading from the volt setting by mistake, didn't seam to hurt it, and since Dave in EEVBlog ep #1292 he connected it to that fence controller and didn't blow it up, so I can't imagine 5V & less then 200 mA sending it to multimeter heaven, and when testing the volts across my load, they match the BM786 perfectly, but on my load, when doing mA the BM235 gives me a reading of about 90.1 mA @ 2.13 v and the BM786 gives me like 77.01 mA @ 2.10 V, the bench top power supply set at 2.3V @ directly off the meter I get 2.400 or 2.3965 depending on which multimeter I measure the voltage out from the power supply. Now, at various attempts the mA varies, TekPower TP1803D, said lab grade, but cheap $50 supply so figuring thats the reason for the mA on the meters being different at different times, but this don't account for why one meter giving almost 15 mA difference. Now another odd thing is the Amp meter on the power supply, even though it is 0.00 display, is matching the meter I hook up to the load, so at this point I am TOTALLY confused. Just for a test to see what happens when I hooked them both up to measure mA at the same time, in series, and now get the exact same reading, in parallel though I get almost 20 mA difference, the BM786 being the lower reading.... ANY clue what the heck is going on here???

[jknightandkarr]

Well got an update on my issue, kinda stupid mistake, even shown in the "What is a Microcontroller" text. My issue was the lack of a resistor on the base pin to the ground. Tried a 56k resistor in and waaaaaaaaay to dim, so added a 27k in and voltage on across LEDs is 1.9599V at an est 22mA between circuit ground and power supply ground!

Since I am getting different readings, I posted on EEVBlog forums about them and learned a bit, inc the amp measuring settings are different for the meters, which explains the difference, so since mA isn't any place near the 600 or 800mA according to BOTH datasheets from Jameco.... yeah good work there, lol but until I get the EEVBlog 121GW multimeter which is assumed to have much better amp reading circuitry,

https://youtu.be/kr7334u0DFw

Thanks for the help!

Joe

[zappman]

Glad you are able to make some progress resolving your issue driving the LEDs . I watched your video, the movement on the BAR display looks neat.

[jknightandkarr]

Thanks Zap. The red LEDs are for KITT's voice display while the green ones are for KARR's voice display. Both sides now have functional driver circuits, next comes microcontrolling it and adding drivers for the remaining LEDs.

[jknightandkarr]

https://youtu.be/UsB2j8es88s
OMG SOO HAPPY TO SEE IT WORK! Couldn't bee happier unless this was totally finished!

[zappman]

It really looks good, with the bezel/front panel over the circuit board

[jknightandkarr]

Thanks. Next it making the arduino work as a vu meter. I got a program to do it, just need to try and hook up the audio source to it.

[jknightandkarr]

I DOOD IT!! The program I found via Element 14 video WORKED! Had todo some changes, but I made it work! My Arduino Uno is now a VU meter! Plus I still have enough pins for the 4 step engine start up countdown, Normal, Auto Cruise and Pursuit PLUS one for my DTMF tones!!

[zappman]

Your, making real progress now, and sounds like your are enjoying yourself working on the project.