How long must the button be held down to start the brewing?

It's a DPST switch that controls the brewing, and it's turned on for about 30 seconds, and then turned off when the brewing is done.

I know this is on a limited budget, but how much are you willing to spend?

Hoping less than $30. I had an old Arduino & LCD screen sitting around and I have that up and running to time the shot (you can see it sitting on top of the machine.)

 

It's a DPST switch that controls the brewing, and it's turned on for about 30 seconds, and then turned off when the brewing is done.


Hoping less than $30. I had an old Arduino & LCD screen sitting around and I have that up and running to time the shot (you can see it sitting on top of the machine.)View attachment 213924

Heck...you have all you need...why not use that?
Use the unused contact at the internal brew rocker switch as a trigger input to the arduino.

 

Post #1 was quite a ways back. But now we hear that an arduino with a display can be available for the project. So at that point, use the spare switch section to open a gate of a counter from a -0.1 second time base. (= 10.00 Hz)That will give the brew time with tenth of a second resolution. which will probably be adequate for all except competition level coffee brewing.

 

competition level coffee brewing

Coming next year at the Tokyo Olympics.

 

Heck...you have all you need...why not use that?
Use the unused contact at the internal brew rocker switch as a trigger input to the arduino.

Because the OP didn't want to go that route...

 

Coming next year at the Tokyo Olympics.

Hey! I accidentally purchased "Competition grade" charcoal for grilling burgers last year. THAT was a big mistake. It burns way hotter than regular. But it seems that all sorts of things are being brought into the realm of competition, probably by those folks with far too much time on their hands. I have seen shows with competitive cooking already So "competition level" coffee brewing could happen.

 

Ok, this works in simulation, I've not had a chance to breadboard this final one, but it should play. It gives a 120mS second pulse on both switch transitions, which works well on my timer.

Just trying to get a parts list together. I have what I think are all the parts in this list here if you could be so kind to have a look and see if it looks OK (already have the 10K resistors)?

 

Just trying to get a parts list together. Only part I'm not sure about is the part labeled 220n. What type of capacitor is that? I have what I think are all the other parts in this list here if you could be so kind to have a look and see if it looks OK (already have the 10K resistors)?

Updated shopping list

I've substituted through-hole transistors (2N3904 instead of BC847, 2N3906 instead of BC857) and added the 4 capacitors, all ceramics

 

Updated shopping list

I've substituted through-hole transistors (2N3904 instead of BC847, 2N3906 instead of BC857) and added the 4 capacitors, all ceramics

LOL... I must have been adding a couple of things to the cart the same time you were editing it as those items you added don't show up on the list?

 

Digikey added my stuff to your list but wouldn't let me reshare it without reverting to the old list - try again now...

or upload this

 

Digikey added my stuff to your list but wouldn't let me reshare it without reverting to the old list - try again now...

or upload this

Great, worked this time, thanks

 

Ok, this works in simulation, I've not had a chance to breadboard this final one, but it should play. It gives a 120mS second pulse on both switch transitions, which works well on my timer.

So in your circuit the S1 in the top left of the diagram is the switch I'm using to turn on the pump?
I'm a bit unclear on where the "OUT" in the circuit connects to in the timer/stopwatch? I have attached a few pictures of my timer and to start and stop the timer it shorts out the inner and outer pads of the push button. The battery (CR2032) reads about 2.3v and across the start/stop button pads it reads 1.5v.

 

My take on this schematic (if this is the one you're referring to) is that S1 is connected to the coffee maker switch, the extra set of contacts that are unused at present. The timer Start/Stop button gets wired either between VCC and OUT or OUT and (that's a) common ground (symbol). I think it's between VCC and OUT that connects to the two sides of the Start/Stop button. And you'll need to get the polarity right. Otherwise it won't work.

 

I am hoping that we will get a report on how well this circuit performs, and possibly even a picture of what the assembled version looks like.

 

@flyboy320 Yes, S1 is the spare contacts on the switch. The circuit is designed to do the same as the original you showed, which is based on a 1.5v AAA cell timer with contacts between Vcc (+1.5v) and the chip input (ie pull up to 1.5v on closure).

Your timer is slightly different. The switches do have a common connection but not to the battery. I'm still tracing out the connections on your pictures. Can you read any markings on Q1, Q2, and Q4?

I'd hold off on ordering those parts in case there are changes to be made...

 

Can you read any markings on Q1, Q2, and Q4?

Best I can tell;
Q1 L6
Q2 M6
Q4 65E9

Extremely small writing on them but I'm fairly sure that's what's written on the top of them (no markings on the sides).

 

Best I can tell;
Q1 L6
Q2 M6
Q4 65E9

Extremely small writing on them but I'm fairly sure that's what's written on the top of them (no markings on the sides).

That's perfect...

 

OK, here's your timer's circuit ... so we need to make a few changes.... As your switches are ground referenced...

 

Ok, here's the revised circuit, connections, and parts list... I've validated it as far as I can, but without an identical timer, I can only say it should work...

Basic circuit as before but other way up. Changes - C2 is now 1uF (from 220n), Q1 & 2 are 2 off 2N3904 - NPN, and Q3 is 1 off 2N3906 - PNP (were 1 and 2 off respectively)



Connections:
Only tricky one is the centre pin of start/stop button. You'll have to blob some solder in hole and introduce a fine wire, maybe 2 or 3 twisted strands from a thicker wire. then tape over it to avoid shorting to battery+



Enjoy

 

Ok, here's the revised circuit, connections, and parts list... I've validated it as far as I can, but without an identical timer, I can only say it should work...

Great, got all the parts and I can get them locally which saves time and $$ on shipping. Only two parts I'm not sure on are the capacitors. As for the 1uf I can get this one, and the 0.22uf I can get this one, or this one. Would theses choices be OK for the caps?

If I can't get the type needed at the above store no problem, I'll just order everything from digikey.