Help with Countdown Lights

[Boncuk]

Currently the clock only makes a single revolution and stops due to a mechanical limit switch. With a 5 minute countdown there needs to be some sort of logic to start and stop the clock motor. But I think I can figure it out using/modifying your circuit. Thanks again!

I wouldn't be against a digital based countdown, but I couldn't find any cheap large displays. Do you know where a large cheap display could be found? Could I make one from a bunch of LEDs?

Hi jfinch,

you might leave your light bulb indication as intended and connect the bulb circuitry to a microprocessor, such as in the attached circuit.

It requires one push button for operation - "START" and stops automatically at the determined count. I just included the "STOP" and "RESET" buttons in case of a false start to restart the circuit before it times out automatically.

Board size is 78X69mm (3X2.71")

Regards

Boncuk

 

[jfinch]

Hi again. I've finally found enough time to get this project done (I hope). I'm trying to follow the circuit using the 4017 counter. I wired the whole thing up on a reuable breadboard and it didn't work so I pulled it all apart and now I'm just doing it in parts to troubleshoot where I'm having problems. I've got the power conditioning (caps), Hall sensor section and 4017 wired up. This is what I'm seeing:

Supply voltage: 12.2 vdc (battery)
Signal from Hall sensor section, Q-1: 0.1 v with magnet near, 10.9 volts with magnet away
Voltage at pin 14 of 4017: 1.90 volts with magnet near Hall sensor, 8.45 volts with magnet away
Everything referenced to ground

Problem is that the 4017 is not counting. It's hung up on Q0. I'm guessing the clock signal is not getting low enough (or high enough?)?

Suggestions?

 

[4pyros]

jfinch; Are you using the circut in post #36? If so the transister should be driving closer to the rails. A 8 volt high voltage maynot be high enough for the clock pin #14 at a supply voltage of 12 volts. Cheak your transister # T5.
Andy

 

[Reloadron]

A drawing would help. However, if you can isolate the clock input to the 4017 (pin 14) and on the breadboard use a wire to toggle the clock between high and low you should see some counting. It may be erratic with switch (wire) bounce but it should do something.

Ron

 

[jfinch]

Here's the drawing I'm (mostly) following.

What should I check on T5? It is a BC547.

 

[blueroomelectronics]

It's the "mostly" part that concerns me.

 

[jfinch]

No need for concern at this point, blueroom. I've not strayed from the schematic at this point.

Things I didn't expect that I'm seeing. I thought the Hall sensor circuit would be more of a 0 volts when no magnet around and the full 12 volts when near the magnet. And I expected similar voltages on the clock input of the 4017.

 

[audioguru]

The transistor that drives the clock input of the CD4017 has its output go to the positive supply voltage and almost to ground. Yours is messed up.

 

[4pyros]

What should I check on T5? It is a BC547

Everything! Is it any good, is it hooked up right, are you using the right resistors,is it hooked up right?

 

[jfinch]

Found the problem. I had T5 wired backwards (looked at the datasheet and thought I was looking at a top view not a bottom view). Everything's fine now. The signal at pin 14 is now 0 and 12 and the counter now counts. Thanks guys.