Hello all, I am relatively new as an electronics hobbyist and wanted some help with design of a circuit.

I am interested in designing and making circuit that operates a 2 digit LED count up timer. The operation will be activated by a magnetic sensor switch to be installed on an espresso machine to time shots. I want the timer to reset to 00 and count up when a solenoid on the machine energizes and then stop counting when the solenoid is no longer energized. I can power the circuit from the 12v available at the controls of the machine or if necessary use an external power source.

Let me know if more information is needed.

 

How rapidly do you want it to count - to advance the digits? You probably want the display to hold until it resets to zero when the next cycle starts? Are you certain it will never need to count past 99?

If it was me, I'd use a commercial timer and wire it to start and stop based on the solenoid power. In other words, I'd avoid messing with building my own clock, display and all that. No point to re-inventing the wheel.

 

The reason for not going past 99 is if a shot of espresso takes longer than 30s it isn't going to be good! If I use a 2 digit timer, I would want it to count seconds. If for some reason I ended up with 3 digit, I would count 1/10th seconds. I had thought about the follow two options as starting points:

https://www.futurekit.com/product/25444/fk926

Seems like a reasonably simple counter and I can wire the display and put it where I want. But can I achieve what I want with reset, start and stop with the solenoid based switch(es)?

https://www.ebay.com/itm/0-8-Red-LE...d=331477528272&_trksid=p2047675.c100005.m1851

Not sure what this counter is capable of . . .

 

The second one doesn't look like a timer which is what you want. Too bad, it looks really easy to mount. Your cutout wouldn't have to be precise because the bezel would cover.

The future kit looks workable but would be a pain to make a really clean mount.

Something like this looks like it would work and be easy to mount. Though, there are a lot of similar ones on ebay or alliex

 

I could figure out the mount for the display on the futurekit fairly easily, but wasn't sure if it would do for me what I want since it has separate switches, start/stop and reset. The ebay and other options I have found so far seem to be 5 digit which would be excessive.

If the futurekit would work, I can go about figuring out how to build the start/stop and reset based on the state of the solenoid.

 

Actually. as I look at it, the future kit appears to be just a counter, not a timer. There's zero information about how it works but usually counters count pulses in.

Here's one that is probably not what you want but if it was a bit smaller (and cheaper)...

 

This one has a stopwatch function and 2 switches that control start/stop and reset . . . I will still have the issue of mounting the display, but it should be easy enough to figure out that part.

 

The link might help...

http://www.icstation.com/mobile/electronic-clock-digital-display-module-electronic-suite-p-2042.html