TIP31C Pinout

 

I think you've found the source of my trouble with the circuit. I can't redo it right now, but I will have the corrected setup done tomorrow morning. Thanks for coming up with that. Silly me for thinking I knew what I was doing.

 

TIP31C Pinout

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Results. It worked! Your suggestion about the pinout was correct. Using the 6-volt wall-wart, I tried the combination three different ways: with both the 10-ohm resistor to the Base and the additional 10k resistor in the R2 position, brightness went from zero to about 70%. I removed the R2 resistor and got a longer stretch of zero, then a ramp-up to about 60%. I removed the 10-ohm resistor to the Base as well, and got about the same results. However, I also switched the wires to the full-power position, and that worked fine. Full power.So I will solder the circuit up and leave a gap for trying different R2 values. Apparently, it wasn't my breadboarding that was the problem. Using the breadboard just made for a lot of flicker in the panel. Thank you.

 

Great

Now remember, you are now at 6 volts instead of 5 so you might not want to use any full power bypass, unless the LEDs can take 6 volts.

When you say 70% of full power, was that a visual observation or did you check the voltage across the LED? (you should be getting 5 or so)

R2 in or out shouldn't change the max value, only the bottom range, your pot may not be going all the way to 0 ohms. (or the supply could be weak and the small extra load is pulling it down)

What is the rating on the 6 volt supply?

I don't mean to go on and on, but you said you wanted to learn.

 

The percentages were visual estimates. I'll start checking the voltage. I understand your caution about the total voltage, and I'll try to come up with some way of governing it. The first thing I want to do is read up on voltage divider circuits to find out more about what I just managed to do with your help. I'll have more questions soon. The 6 volt supply is rated at 500mA. Am I expecting too much of it?

 

Well, the LEDs are rated @ 3 watts so @ 5 volts that would be 600mAs, so yea, it's under rated.

Your total output voltage with a 6 volt supply should be no more than 5.3 or so, which will be fine.

6 volts minus the drop across the transistor (about .7 to 1)

 

I may have a stouter wall-wart here. If not, I'll get one.

 

As a humorous aside, I tried the heavier-duty wall-wart and I could only get about a single volt out of it. Considering that it was built to power a Zip drive, dating it to pre-2000, I suppose I shouldn't be surprised. I never throw anything away. I ordered a new 5 volt PS.

 

Are you ordering a 5V or 6V supply?

 

5 volts.

 

Hello, I have one-I hope-last question. Find attached a re-interpretation of the schematic for the transistorized controller. As it is now, the pot turns counter-clockwise to increase light coming from the LEDs. I can live with that, but I would prefer that it turned clockwise. Could I accomplish that by simply flipping the pot connections left-to right, or is it more complicated than that?

 

Give it a try

 

I figured that with the LEDs in the collector side, the transistor acts as an amplifier, so LED current will be Beta x Base current. Add a resistor in the ground leg of the pot so minimum wiper voltage is about 0.5V, and the sweep of the pot should go pretty much from full off to full on.
5V is close enough to 4.5V that any driver from a flashlight that runs on 3xAA cells should be fine at 5V.

 

If the LEDs are on the collector side of the transistor then the high voltage gain of the transistor will make the dimmer pot act like an on-off switch with dimming happening only at a tiny spot on the dial which changes when the temperature changes (as it warms up from being turned on).

 

Give it a try

It worked. A complete range, from dark to bright. Clockwise. Thanks.

 

It worked. A complete range, from dark to bright. Clockwise. Thanks.

ElectricSpidey, Bernard, et al., in case any of you were interested (probably not), I haven't given up, stopped, lost interest, or moved away. After a series of unsuccessful attempts to build some old kits I've had since forever, after seeking comments about my lack of success, I stopped building circuits temporarily. I've ordered a more powerful soldering iron and invested in things like flux, lead-type rosin core solder, all stuff I didn't know enough to use previously. I also started watching YouTube videos about soldering. So I'll be back.

 

Many You Tube videos have made by people who know nothing about what they are showing. They make the videos so that You Tube pays them each time a gullible person sees an ad for something before the video begins.

Soldering? They incorrectly show a height too low that the solder must be dripped into the solder joint.

 

Thank you for the cautionary note.