randytsuch wrote:For some reason, its hard to find examples of pulse count in the arduino/esp32 environment.

Does it even support it? I've used the feature with an Atmega328 but had to program the registers directly.

randytsuch wrote:I'll try it at some point, but at the rates I'm at, interrupts are no problem.

Of course, no need to go out of your way to make it complicated if not needed.

randytsuch wrote:I also wonder if there is some air in the lines, throwing off rates and volume early.

How do you know it's off? It seems like determining the flow by weight in the cup early on is complicated since the puck is absorbing water and at the same time losing mass.

jpender wrote:Does it even support it? I've used the feature with an Atmega328 but had to program the registers directly.

From the link I found, someone got it working. If I get a higher count digmesa flow meter, I think it will be useful.

jpender wrote: How do you know it's off? It seems like determining the flow by weight in the cup early on is complicated since the puck is absorbing water and at the same time losing mass.

I track weight from a bluetooth scale, and volume based on flow rate, and record everything once a second. I'm saving weight, rate and volume, as well as some other stuff.

I also reset a timer when I see the first drops of the shot come out, so I know when flow started.
I've been using 19 grams in, and I get to around 40 ml of volume when flow starts. Pretty consistent.

I expect around 20 ml, one to one. I've weighed the puck after the shot, and was close to double in weight from what I started with.
I don't know if the amount of water in the puck changes as the shot progresses, have been assuming it doesn't.

Randy

I guess I misunderstood you. I thought you were having problems reconciling the difference between what your flowmeter told you and what your scale said during the initial part of the shot.

If it's the whole shot that isn't adding up maybe you're making an accounting error?

Hot water is a little less dense so 40ml might be 38 or 39g. That's a minor correction that you might not care about.

If the wet puck weighs 38g and the dry dose 19g that doesn't mean you have 19g of water in the puck. There's less coffee in the puck after the shot is finished. For example, if your extraction yield were 20% there would be only about 15g of coffee left in the puck. In that case the puck would contain 23g of water.

The coffee in the cup will also be of higher density than water.