Need a timing circuit for motor contol 1

[crunch53]

Could someone help me with a circuit I’m trying to make. I have a geared motor that’s 3 volts. I’m not sure of the current right now. If I push a micro switch I want the motor to either make a certain number of revolutions or stay on for a certain amount of seconds. This should only be able to be done maybe 2 to 3 times every hour or 2 or the micro switch is disabled until that time. There should also be an led that is lit whenever the switch can be pressed. If possible the times should be easily adjustable.
Any help would be appreciated.

Thanks,

Mike

 

[itsmoked]

From what little you have devulged.. I can only recommend that you look into PICSTAMPS.

http://www.parallax.com/html_pages/products/basicstamps/basic_stamps.asp

http://www.phanderson.com/stamp/stamp-pic.html

 

[bill318]

This can also be done with a PIC 12C671 or 12C672 or an AVR Tiny(all 8-pin devices). Use an A-D input to read the wiper arm of a pot to control the run time. Use a GPIO pin to drive a low side FET to run a little DC motor (assuming this is the type of motor you are referring to). Use another GPIO to sense your micro switch and yet another GPIO to drive the LED.

If you are not into programming, use a simple LM555 timer in one-shot mode and drive the gate of the low side FET with this.

The LED is easy if you are driving a small DC motor with a low side FET. Connect the motor + input to B+, FET drain to motor -, FET source to ground. Connect the LED current limiting resistor between the FET drain and the Annode of the LED. The cathode of the LED to ground.

Any time the motor is running the drain will be near ground potential and the LED will be off. When the motor shuts off, the Drain will be at the B+ level via the windings of the motor and the LED will turn on indicating it can be triggered again.

-Bill-

 

[crunch53]

Here is a little more info for you.
It doesn’t need to be real accurate.
Time or revolutions will work but I think I would rather have revolutions to control it better. Like I say it is a geared motor so let’s say that I want an led sitting next to the micro switch. The led is on right now. I push the switch and the output shaft of the motor turns 3 times and stops. 45 minutes later I do the same thing again. The circuit is set to do this only twice in 2 hours. So now the led goes off and the motor will not run either. 2 hours has passed since the beginning and alls well. Now the led is on and the switch can be pressed 2 more times in the next 2 hours. The motor I’m working with right now is running on 3 volts. No load is about 100 milliamps and with a load I can get it up to around 300 milliamps.
I was thinking about a 555 also with a few other parts.
I would love to try those PICs. I’ve heard of them but that’s about it. (I know enough about some of this to be dangerous) There are so many things I would like to do that I think those things would be perfect for. I would imagine the programmer and the software is fairly expensive and then there’s the old learning curve.
Thanks for your help.

 

[bill318]

OK, that is a bit more information to work with... The PIC firmware IDE is Free from Microchip or ATMEL for that matter. When programming these little guys in assembly, there are not too many instructions to learn. The programmers are not too expensive at all or you can roll your own. The PICs mentioned above are OTP parts, but you can also buy an EE part for code development.

Given the new timing requirements you describe, it would take two LM555s (or you could use a LM556 dual timer).

Now the hard part, the Revolutions counter. There are a couple of ways to do this, one is to place a micro switch or hall sensor to sense the revolutions and then plumb this into your micro. Another harder way is to sense the brush noise of the motor (if it has brushes)and count the number of commutation polarity swaps. This would require an AC coupled amplifier with filtering to get any useful signal and then have the micro count the pulses required to have the gear motor turn the required revolutions. I think the external sensor or the timed method would be the easiest.

Good Luck, Bill

 

[felixc]

If you want a cheap development kit, you can get for $40 a development board, onto which you can add your interface circuit, a full C and assembler compiling environment, and a download/debug cable. This is for the Zilog Z8Encore. Lots of code examples, usually the best way to start and reduce the learning curve.

But, yes the whole thing can be done with 555s. So it depends if you want it quickly and for cheap, or if your want to use it to start building experience.

 

[coconutalley]

I would just buy a digital encoder and attach that to the shaft. Use the output signals to derive position and speed information.

The other way is to use one of those multiturn pots
[probably geared] and attached it to the shaft. Just measure the change in [resistance--which would be a voltage] to know distance traveled. A comparator circuit or a little pic can do the controlling.