Double check for wiring errors. All it takes is one misswire for it not to work. That's the most common cause of a breadboard circuit not working.
Edit: One way to check wiring is with an ohmmeter while marking off the measured connections on the schematic with a highlighter.
Need Help recreating circuit with 25 year old schematic
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26th May 2011 05:03 PM #1circleofcircuits
Need Help recreating circuit with 25 year old schematic
Hey guys,
I am new to this board and to electronics in general. When I was a little kid back in the 80s, my uncle built me a little box that, on the outside, had only an 8 segment LED array, a rheostat and an on/off switch. The box simply controlled the LED array and the circuitry made the LEDS go back and forth, The rheostat would control the speed of the back and forth motion.
Long story short, my uncle passed and in cleaning out his stuff, I found the schematic he drew to build the box for me. I no longer have mine but I want to build another one, and I want to build it exactly the way my uncle did, using the same components. I'm sure things have improved in 25 years but I want this just the way he built it.
I have all the required components (ICs, pot, capacitors and resistors, etc) mounted on a solderless breadboard, but I can't for the life of me get it to work. I attach a 9v battery and only the first LED lights up, even if the potentiometer is disconnected!
If you guys could guide me through this, it would mean a lot to me. I've attached a pic of the schematic (cleaned up a bit as some was hard to read) along with some pics of my breadboard.
Thanks,
KyleLast edited by circleofcircuits; 30th May 2011 at 06:15 PM.
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26th May 2011 05:09 PM #2crutschow
0
Last edited by crutschow; 26th May 2011 at 05:11 PM.
Zapper
Curmudgeon Elektroniker
--Inside every little problem is a big problem trying to get out.--
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26th May 2011 05:25 PM #3MrAl
Hello,
I was going to ask what kind of test equipment do you have? A meter?
The way to trouble shoot this circuit is to start with the oscillator and make sure it is pulsing, then make sure the decade counter outputs are pulsing, then make sure the decoder outputs are pulsing. In other words, stage by stage starting with the first and progressing to the last.
If the pulse period of the oscillator is long you should see the meter reading jumping up and down. If it is short, you'll see some value that is about midway between the positive voltage rail and ground.
I dont see any bypass caps either. You may need those if you get erratic counts once you get it working.0Last edited by MrAl; 26th May 2011 at 05:35 PM.
One test is worth a thousand expert opinions, but one expert specification is worth a thousand tests.
If i miss something you posted or something you think is important, feel free to PM me.
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26th May 2011 05:42 PM Thread Starter #4circleofcircuits
I have a multi-meter and will try the suggestions above. Can someone compare the potentiometer on the breadboard with the schematic and see if i set it up properly?
Thanks,
Kyle0
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26th May 2011 05:59 PM #5SABorn
For starters 1 side of your rheostat is not connected to any thing, have another look at the schematic all 3 legs are shown as connected.
Otherwise your wiring is too much of a mess for me to follow and my eyes became knotted attempting it.
Pete.0
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26th May 2011 05:59 PM #6carbonzit
Pot looks OK, at least so far as one can tell from the photos.
I'm wondering about some of the unconnected pins of the chips. If any of these are inputs, they would be "floating" and could cause problems. All unused inputs should be tied either to ground or to V+.0
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26th May 2011 06:01 PM #7carbonzit
Doesn't make any difference. A pot connected as a rheostat with 2 connections works just the same. Think about it.
Originally Posted by SABorn
(Some folks like to tie the unconnected end to the wiper for safety purposes, but that's way overkill here.)0
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26th May 2011 06:08 PM Thread Starter #8circleofcircuits
I've studied the data sheets for the chips and some of those connections are marked "NC" (not connected) but I think a couple had a purpose...so those may need grounded...
Kyle0
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26th May 2011 06:10 PM #9carbonzit
If the unconnected pins are NC, don't sweat it.
If they're inputs that are active high, tie them to ground. Active low, tie them to V+.
If outputs, don't worry about them.0
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26th May 2011 06:10 PM #10wkrug
First i would do is to increase the Capacitator C1.
That will slower the Oscillator and give you the possibility to measure with your Multimeter.
Then check the pulses on PIN4 of 4049. Are they present ?
If this works the 4510 should count.
When this is working you can check the 4028 decimal decoder.
The acording output of binary bit pattern of the 4510 should be active.
When this all is working Led line should light up minimal once.
The last in this Chain is the 4013 that shoud create the UP/Down Signal for the 4510 when end of LED ladder is achieved.
If one thing in this Chain wouldn't work ckeck Power an Reset signals of that.
In C-Mos technology no input! can be leaved open - It always must conected with a fixed Signal ( GND or VCC ).
If you don't do that is is possible, the Chip is oscillating on an high frequency.0
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