01 02 03 DropBOB Designs: Cold Drip Coffee - THICK AND RICH! 04 05 15 16 19 20 21 22 23 24 25 26 27 28 31 32 33

Cold Drip Coffee - THICK AND RICH!

So here's a progress update on the development of my cold drip coffee machine. After my last post, I had determined that the only way to get this coffee just right, was to control the drip rate. 

The idea was to use either a photo-interupter or a pietzo electric disk to detect the drop. Since I need the servo to be used for feedback control (think back to your "Control systems" classes). If I did not have any feedback control, even after perfectly setting up the drop, the drip rate (DPM) would become less and less as the volume of water above the valve becomes smaller (simple fluids 1 class, of which I had to take 2x because of a terrible teacher & an overachiever's workload).

So, as Lee's Electronics nor Main electronics had any readily available photo-interrupters, I settled on the pietzo sensor ... It turned out to work, but it happened to skip every third drop or so ... "Not good enough!"

So, I turned to my next favorite electronics distributor Digikey. I used them for work to purchase the odd chip here and there and just love how cheap and fast they are. I ordered the GP1A57HRJ00F photo-interrupter and received it the next day as I got home from work. 

So off to the grinds I go (literally). I held off on cleaning my room as you can tell, I was just so excited to make this new sensor work. And work it did. Really well too. This thing has a 1-microsecond response time ... that is really really fast.

So after throwing together a cheapo setup using my trusty wood clamps and some junk around my shop, I managed to get a reliable, easy setup.

As of this writing, I'm at 8483 drops and 16-hrs ... bottle is only about half way filled (see first picture). My controller is set to 8-DPM and averages around 8 to 9 due to the play in the servo. But it really does work.

 Just look at this thick, sludge of a coffee. I haven't tried it yet, but I have a feeling I'll need to dilute it ... Its just so THICK!

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