Johnson777717

I need some advice if I may:

I'm trying to design a circuit but I'm not sure if a microcontroller, or simpler logic IC's would be best in the situation. I don't have the specifics of the design yet, as I am still in the "concept" stage of the design process.

Here is the concept.
1. Powered by 110VAC to DC. The DC values depend on what the circuit would demand.
2. An IR LED send / receive beam is established, normally ON.
3. When the IR beam is broken by a physical object, the circuit will wait 5 minutes or so, then the circuit drives a motor in a specific direction until it reaches a stop point.
4. The stop point signals the circuit VIA a mechanical switch. When the first stop point is reached, the motor reverses until the second stop point is reached.
5. When the second stop point is reached a switch signals the circuit to stop the motor, then the circuit resets the IR led beam and waits until the beam is broken again.
6. If the beam is broken again, the cycle repeats steps 3 through 6.

The application. I have an old cat litter box, which automatically scoops the waste into a holding tank, and thus cleans the litter box each time the cat has used the littler box. I can't find any datasheets on the IC's involved in the original circuit, so I'm clueless as to the current operation of the IC's etc. I'm assuming that the IC's are custom made for the manufacturer, and thus, information about the IC's aren't available.

I'd like to re-design the circuit, using known components, for the same concept. The original circuit overheated, which burnt up pretty much everything. The power supply LM317 wasn't heat sinked, and due to continuous use, the LM317 eventually failed, and burnt up some capacitors, a few transisors etc. The circuit is in pretty bad shape, so I'm deciding to start with a new circuit.

Does anyone know of a circuit or two that uses similar concepts, or part of the concepts that I can piece together?

I appreciate your assistance. Have a great week!

FRED6298

From your message , I am not convinced that the original is not salvagable. Are you able to read any part numbers on the transistors that
fried ? Did you try to replace the LM317 and capacitors?

Doe the 'IR' beam and detector still work ?

tavib

The use of a small uC like PIC16F84 is cheap and simple.
The hardware logic become too complicated in this case.

Johnson777717

Thanks for checking I did replace the obviously fried components. I replaced the LM317 and a LM7805 regulator as well as four other transistors. I cannot remember the original part numbers, but they were equivalent to the NTE123AP transistors. I've checked all of the pin outs of my replacements etc. I also replaced a 100nF ceramic disc cap, and all of the electrolytics (I think there were about 5 or so, including the power supply capacitor, 2200uF) just for good measure. After doing so, I checked my work, cleaned the flux from the board, made sure nothing else was shorting and fired it up. It didn't work, so I assumed that there was a problem with the IC's (One has a 4MHz crystal, so I'm assuming it's a microcontroller.) From that assumption, I decided to start a new design. I don't have a scope, so I can't go poking around.

Would you have any ideas on what to check next? I have some pictures on my computer at home, and I can post these at lunch time.

Thank you VERY much for your time, and assistance.

FRED6298

WOW ! You have gone the distance.
Do you need a NEW 'IR' link ?
To start, you need to define the requirements for IR link for Part 'A'.
1. What is the distance from emitter to detector ?
2. What power supply do you want to specify ? (12V or 5V)

Part 'B'
1. Do you want to use a microcontroller ?(a single IC solution) If so,
What ?
2. Do you want discrete logic ? If so, 2 I.C.'s (a 555 timer and F/F)
will work.
Part 'C'
1. Will you need a motor driver ? Are the motors O.K. ?