Re: Help with 3 stage timed controller


T313C0mun1s7 wrote in message ...
I am hoping some of you can might be able to help me with a circuit
design (by basically designing it for me since it has been 12 years
since I even attempted any type of circuit design). Any help would be
greatly appreciated.

I have a vacuum conveying device that sucks regrind out of a
granulator and dumps it in a box. The control circuit was designed in
a project box by someone other than myself, and seems to consist of
discreet components on a breadboard. It is analog and requires a lot
of time playing with it to get the timing right, and it is working
only intermittently. I wish to replace it with a new control circuit.

The operation of the old control circuit (so you know what I am
replacing and the function it is performing) is as such: In the box is
a transformer to provide the low voltage DC as needed, there are
relays are running a vacuum pump and opening a solenoid controlled air
valve. The cycle is
1) run vacuum for time determined by a potentiometer (and guess for
how long it will run) then puff air to clear granules and dust.
2) after a delay determined by a second potentiometer - restart cycle.

The current problems include the fact that times are hard to set with
any consistency, and that if the delay time is too short it will
restart the vacuum while the eject air is still going. Thus I consider
this a 2 stage circuit.

What I would like to build is a 3 stage circuit that has a vacuum
stage, an eject stage, and a delay stage. I would also like it so be
digital so the times are predictable and consistent. Here is what I am
trying to create.

Stage 1) Vacuum - close relay that runs the vacuum pump for the time
(in seconds) set on a two digit thumb wheel, then advance to next
stage.

Stage 2) Eject - close the solenoid that open the air valve 5 times,
on 5 seconds off 3 seconds, then advance to next stage.

Stage 3) Delay - wait for a time in seconds set by a two digit thumb
wheel, then start over at stage 1 again.

The thumb wheels can be displays with up down buttons or whatever, I
don't care as long as I can set seconds from 01 to 99 easily with a
clear readout. Please specify the type of output for the thumb wheel,
single pole changeover, BCD or whatever used in your circuit.

Thank you very much for you help.

Google sequential timer
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