Introduction: The 7$ Coffee Grinder Timer

Since I was infected by the espresso virus, I felt the need to buy a professional espresso machine and a good coffee grinder to get the best result possible for my personal needs. This is my solution for a good espresso on a budget.

First, I had to get an espresso machine, which was fairly easy after some research and a few days waiting to get a good deal on a used machine. I picked the Gaggia Classic because it can do everything I need for under 200$ and it also looks quite good and old-school. But now there comes the hardest part - the coffee grinder. It is nearly impossible to get a good deal on a used professional grinder so I had to find a machine in-between which can do the job. So I looked on eBay and got a Graef CM 800 grinder for 80$. This model is ideal referring to the grinding degree but it has one caveat - it has no built-in timer! So after a few minutes, I realised I need to get a timer for consistent results and I started thinking about how I can get one. Now I would like to share my solution to the missing coffee grinder timer problem with you.

Total cost

I managed to build my timer for about 7$ because I had a lot of stuff laying around in my house like the USB charger, the resistor, the potentiometer knob and some old cables. If you bought everything new you could expect a total cost of about 10$ to 20$. But all in all, these expenses are nothing against buying a new professional coffee grinder with a built-in timer.

Things to keep in mind

I am showing you how I customized my coffee grinder, I am not telling anyone that he/she should do the same with their coffee grinder! Everyone is responsible for what he/she is doing!I am not responsible if you hurt yourself, torch your house or anything that kind trying to create your own coffee grinder timer! You are doing everything at your own risk!

Also, keep in mind, that the prices of the parts change frequently - this means that my information in this Instructable could get off-track over time.

Step 1: Materials

Step 2: Circuit

Note: I used a normal Solid-State Relay in the sketch, but I am actually using a SSR breakout board, which also requires another 5V cable, which is not included in the sketch.

Step 3: Wiring

Solder everything together and seal the solder joints as well as the whole Digispark with hot glue.

You may also have to grind away a few millimetres of the USB charger like you can see on the picture to ensure a good power connection.

Step 4: Programming

Just copy my code, which can be downloaded from my GitHub page, in your Arduino IDE and upload it to your Digispark.

Note: To use the Digispark in the Arduino IDE you have to install the Digispark Arduino package first!

Step 5: Disassembly

Disassembling is quite easy, just remove all screws you can see on the top and bottom and after a few minutes, you are left with the housing and motor.

Step 6: Assembly

Now take out the two screws, which hold the plate where the power switch is attached to, and drill a hole for the potentiometer. You also have to grind away some of the plastic of the power switch holder to fit the potentiometer.

Now all that's left is connecting the Solid-State Relay to the grinder motor and the front button to the Digispark.

Last, install the power connection, screw everything back together, and you are finally ready for your first espresso!

Note: I also shorted the upper limit switch to get more free space inside the grinder, but keep in mind, this removes a safety feature of the grinder, so do this at your own risk!

Step 7: Conclusion

I think I found a proper solution to create consistent espresso results without spending a fortune on equipment.

Please feel free to adapt my idea and code to your needs. I would be very grateful to include your improvements!

Thanks for your support! :)

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