Yet another DIY grinder timer (<$100)

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Postby redpig » Sep 17, 2012, 11:28 pm

The fruit of this evening's labor yielded a timed outlet for grinder use that is accurate to 0.01s for less than $100. If you don't mind wiring a wall sconce but soldering isn't your game, then this may be right for you!

[EDIT: Follow this post at your own risk! I am not an electrician or particularly good with hardware. Proceed at your own risk!]


Time: took me ~90 min . . . after the parts were delivered

  • stripper
  • multimeter or continuity tester (optional but recommended)
  • drill; bits based on cable sizes
  • phillips screwdriver (cross-tip)
  • electrical tape (optional)
  • scissors (unless your stripper does it all)
  • push-in connectors: (2) three wire, (1) two wire


(note, most cables have a AWG rating printed on them. You should make sure the amperage/wattage of your grinder works for the cables you have and for the timer relay above. If it doesn't work for the latter, adding this doesn't seem impossible.)

Components I wish I'd bought:
  • Any sort of power switch, there's no need to leave the timer on...

What I had on hand:

  1. Remove the front and back plates from the enclosure
  2. Remove the outer insulation from your power cables (no more than 6")
  3. Determine if all the wires will fit through the existing 1/4" hole.
  4. If not, grab your drill bit and, if possible, variable speed drill and ease your way into a new hole.
    I drilled one new hole and expanded the existing hole.
  5. Slide the timer into the front plate and push the cables through the holes in the backplate such that some of the outer insulation is on the "inside".
  6. Add some electrical tape (or whatever) on the inside to keep the cables from pulling back out. A poor-man's way to offset any tension on the cables later.
  7. Using the continuity tester, ensure the internal wires on both cables match the outlet as expected. For me, it was green:ground, black:load, white:neutral.
  8. On the grinder-side, strip less than 1/4" of wire. Screw it into 7 between the plates (remove the screw+plate entirely and slide in.
    (Note, you can get hook connectors. I did, but I got ones that were too big, so I went without. If you strip a small enough amount, no wire will be left exposed.)
  9. Strip both the ground wires about 1/8". Join them with a connector. You're done with ground so if you want, you can trim them back.
  10. Take the neutral on the outlet-side and cut it in half.
  11. Take the half and strip both ends and the outlet side ~1/8"
  12. Strip the neutral on the grinder side ~1/8"
  13. Join the grinder neutral, outlet neutral, and loose neutral with a three-wire connector
  14. Take the one loose neutral end and screw it into terminal 9.
  15. Similar trick for load: cut the exposed outlet load wire not far from the larger insulated area -- maybe keeping an inch.
  16. Cut the loose load wire in half.
  17. Strip both ends of the loose load wires and the original load wire as well.
  18. Screw one end of a loose load wire into terminal 8.
  19. Screw one end of the other loose load wire into terminal 10
  20. Join the three available load wires: 8, 10, and outlet with a 3 wire connector.
    (Review the PDF for the ASL-51 on the Auber website to make sure your wiring is correct!)


uh. that's pretty much it :)

Prior to boxing it back up, I suggest some validation:
  1. Check the continuity from terminals-to-outlets for both cables
  2. Plug it all in and connect a lamp to the grinder-side.
  3. Program the timer to function 02, relay mode 04 by holding > for 10 seconds.
  4. Once it quits flashing, it will drop you back to where you can set the time in 00.00s using > and ^
  5. Set the time, then hit RST to set it off. The light should come on and stay on until the time runs out.
  6. If so, box it up! If not, ?????


I've used it all of five times so far, so here's hoping it lasts! :D

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Postby LasFumas » Sep 18, 2012, 12:31 am

Wow! Thanks for the instructions for us non-techie types. To me this seems like a no-brainer once you have the dose figured out for your machine. For me, it really opens my future grinder upgrade path quite a bit as I find leaving the hopper with a day or two worth of beans the most convenient. I'm going to print this out so I have it when the time comes. One question though, does the timer remember the time you previously had set when it is turned off?

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Postby redpig » Sep 18, 2012, 1:50 am

LasFumas wrote:Wow! Thanks for the instructions for us non-techie types.

I hope it is useful! I kept eying arduinos/etc, but it seemed like a lot of work :)

LasFumas wrote:One question though, does the timer remember the time you previously had set when it is turned off?

It has in quick tests. I'll report in if it gets forgetful overnight though.
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Postby dino » Sep 18, 2012, 6:45 am

Hi redpig,
your project looks like the project I did a little while ago - converted a DRM conical/flat burr grinder to a doserless grinder with a built in timer. I cut the dosing chamber off , had the coffee exit spout machined flat to accept the doserless spout ( from a Anfim Caimano - donated by Espresso Company Australia :lol: ) added some food grade rubber to slow the coffee down & get rid of the static , removed the relay , cut the hopper shorter etc etc. haven't finished with the panels to cover the front opening - waiting for a friend that has access to stainless steel and a workshop to get back to work so just using the flimsy aluminium for the moment.
I have named it a dinolab - the versalab that I can afford :lol:

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Postby bostonbuzz » Sep 18, 2012, 8:13 am

Great post. This looks pretty easy! I was also wondering if I could use bare wires when I wired up a PID that's lying around since I've seen everyone else use fancy connectors.

I thought for sure that the first shot of Dino's grinder was an espresso machine with some beans tossed into it. hahaha.
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Postby redpig » Sep 18, 2012, 10:24 am

The dinolab looks great. I'd love to head down the same path you did, and I'll definitely be using your post as a guide! Aside from hacking up the hopper, I've been nervous to do anything more invasive for fear starting something I can't finish, but your mods are encouraging.

Did the food-grade rubber get rid of the need for an antistatic gate? It seems like a cool idea and a departure from what I've seen before. I also like that you didn't end up with a giant doser-cone like the Mazzer doserless.

Out of curiosity, how'd you cut the hole for the timer? That was one, of many, reasons I went with an external timer for starters.

Thanks for sharing!
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Postby dino » Sep 18, 2012, 10:37 am

redpig , the hole was cut with my trusty dremel and about 6 cuttings discs! then some fine tuning with needle files so that the fit was nice & snug. I am happy with the result even though it sounds like a Russian tractor when it is grinding :lol: , and with the food grade rubber it was trial and error to remove " fingers" that I cut into it - end result is there is just enough back pressure to stop spraying and eliminate static.

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Postby redpig » Sep 18, 2012, 11:39 am

dino, Hardcore! I wasn't sure if the dremel was up to the job -- I, uh, burned out my dremel turning a double-sided aluminum tamper into a single-sided one. I guess it's time to buy a new one! But for now, I'll break in the timer in its own box :)

The food grade rubber idea is still blowing my mind. Awesome.
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Postby redpig » Sep 18, 2012, 2:55 pm

Hrm I just realized my grinder may be over the recommended switching load for this timer. So I may have to get the external closed relay, but for /now/ it is performing fine. Other timers I've looked at go up to 1/3 hp, but the Auber seems to be 1/10 hp. (My guess is that my grinder is 2/10 hp. Doh.)

Edit: I misread (again) -- it says rated at 1/10 for inductive loads, so I think my 1.3a grinder is still in spec. I'll ask Auber for clarification, just in case. If I end up adding an extra relay, I'll detail my misadventures here, of course!
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Postby redpig » Sep 20, 2012, 11:20 pm

Thanks, Grant -- those are great tips! The enclosure originally came with a grommet, but it didn't leave enough space :/ It didn't occur to me to order anymore. I'll update the instructions to include deburring with optional grommets. Using cable ties is genius too! But your comment about "sticky residue" made me remember to fold the electrical tape on itself (to make it not sticky) before wrapping the metal parts of any contacts that I was fiddling with today . . . which leads me to a quick update!

I added a three-way toggle switch and a 1/2 HP relay. Aside from the cabling being a bit more complicated, it works! My fear was that I'd either burn out the built-in timer relay or have some sort of surprise SPARK because the rating on the timer seemed like it might not be quite high enough.

The instructions are now slightly more complicated, so I'll include a wiring diagram and more pictures in an update. For those who are impatient, I purchased:
A. An Omron LY1 AC110/120 Miniature relay: It is small enough to fit in the case, it's coil circuit is 110/120v, so it can be powered via the timer relay (where the grinder is hooked up in the v1). Additionally, it is rated for 1/2 HP at 120 (or a 35a in-rush and a 7a current). It'll work for many(*) grinders except beasts like the Major or the Robur :)
B. A 3/4 HP rated on-off-on toggle switch (maintained). I wanted to be able to turn off the timer when I'm not using the grinder. I wired the timer power to the up direction, and I wired the down direction to the relay coil. This means that when the switch is down, the grinder is on -- no timer. When the switch is up, the grinder is timed, and in the middle - it is off. (Technically, the relay has power, but it is open.)

This leaves the price still under $100, but it's getting closer... which is still cheaper than a 100th of a second accurate dark room timer!

Anyway, I'll try to write this up in a way that makes sense. If you want to time a grinder with a higher HP/wattage, you'll need a a higher rated relay and switch - but the price difference is only a couple of US dollars and the wiring will be the same. It may just be a slightly tighter squeeze or need the bigger Auber enclosure.


* - my grinder is 1.3a at 120vac so ~156 watts. 1/2 HP @120VAC is just over 300 watts, I think, so that should cover the CMH, mazzer mini, super jolly, etc. That said, I can't claim to understand this well enough to make any guarantees that I am right or recommending a safe course of action!
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