Electronics > Projects, Designs, and Technical Stuff
Need help designing a load selector!
WyverntekGameRepairs:
So, I’m stuck. I’m trying to control LEDs using a decade counter that drives some transistors, but I just can’t seem to get it right. I need help!
What I’m trying to accomplish is a circuit that controls a set of LEDs in such a way that if you press a button, the counter would trigger the next output and illuminate the next LED in the sequence (of course through a transistor, since the chips themselves can’t directly drive heavier loads more than about 10mA). Here is the sequence I am going for:
Red, Green, Blue, RGB, Off.
Im using the transformer of a small digital alarm clock, and since I want to run both the clock and the LED circuit on one transformer, I need to keep the power consumption of the LED driver circuit as low as possible.
My theoretical idea was that by using a resettable decade counter, I could have one input and several outputs, which the counter would progress to the next output in the sequence when I pressed the button. I would use the secondary counter, controlled by the final output, to reset the counter and turn all LEDs off until the button is pressed again.
“You stupid fool, use a Raspberry Pi or an Arduino!” Well I would but I do not have one. Besides, I’d like to get more into logic circuits and the raw functionality of them.
I don’t have schematics that are useable. The two failed attempts to draw a schematic had the logic improperly wired, it wouldn’t work as I expected it to when I breadboarded the circuits.
The logic chips I have in my inventory that I could use are:
Ne555 (x2)
74LS74A
CD4094BE
MC14520 (that’s the decade counter I tried to use)
SN74196N (x2, and those are also decade counters)
74LS157N
MC14013B
HEF4053BP
SN74LS123N
I appreciate your help.
MarkF:
Okay. I'll take a wack at it.
Without any logic gates, you will need to press the switch 5 times to get it started.
And there may be an "All Off" state before it starts over?
WyverntekGameRepairs:
--- Quote from: MarkF on May 29, 2020, 07:32:39 pm ---Okay. I'll take a wack at it.
Without any logic gates, you will need to press the switch 5 times to get it started.
And there may be an "All Off" state before it starts over?
(Attachment Link)
--- End quote ---
Let me build this circuit and see if it works.
And yes, I’m hoping that it has an “all off” before the cycle repeats.
Also, I have an additional output for the colour-changing RGB LEDs, you probably didn’t notice that listed. I listed it as RGB.
MarkF:
If you use the SN74196 counter "Load" feature to preset the value to '4' would get
it to start up with the Red LED being ON.
Use an RC time constant on the LOAD pin at power ON to do the preset.
WyverntekGameRepairs:
I’m assuming that it would be wired differently too?
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