Repeat Timer Hacked For 35 Minute Hydroponic Cycles

[GrowColt] shows you how to modify a lamp timer for use with hydroponics. You can pick up this type of mechanical timer at most local big box stores for around $5. The timer plugs into an outlet, and the device you want to operate plugs into it. [GrowColt’s] end goal is to make the timer repeat every 35 minutes, routing power to the connected device for about 50 seconds each cycle. It will operate the pumps and misters in his hydroponic garden to keep the plants hydrated and keep the nutrients flowing.

We’ve embedded his detailed process after the break. It’s not all that difficult, requiring a few common hand tools, some glue, and rubber washer. There’s a gear box inside which controls the timer. Reorganizing that gearing makes it repeat more frequently.

Not into hydroponics, but looking for watering help with your greenhouse? Check out this system which monitors water sensors and dispenses H2O accordingly.


29 thoughts on “Repeat Timer Hacked For 35 Minute Hydroponic Cycles

    1. I’d guess he shortened the shaft because the hole in the topmost gear doesn’t go all the way through, but is only just deep enough for the length of shaft it went over as manufactured. Assuming that’s the case, if he didn’t make the cut, he wouldn’t be able to put the composite gear all the way back down the shaft into the socket the lower gear came from.

  1. I went into a hydroponics store once because I thought it might be cool to grow my own vegetables indoors. Now the state police fly over my house all the time. I liked it better before 9/11 when we still had some presumption of innocence. Now you can’t even buy cold medicine without someone somewhere running your name through a database. Yaay… freedom.

  2. So is this now an open hardware project? I see another Ebay seller is offering essentially the same thing for 2 bucks less, competition can be a beotch. Not to take away from the hack, but plugin timers that can be set at 15 minute intervals are available. In the event timer has to be purchased, why not purchase one of those? Is there something magical about the 40 minute timing interval that 5 minutes would make a difference?

      1. But, to support N0LKK’s point about careful shopping, I recently bought an electronic version of a 24-hr lamp timer for $2 at a dollar store, and it can be programmed with 20 pairs of on-off settings, to the minute. That might suit hydroponics applications.

        It’s pretty much like the mechanical version, plugging into the wall, with one 2-prong outlet on the side. It has 7 buttons and an LCD for programming (like a VCR), and trickle-charges an internal battery to retain settings over power failures.

    1. You don’t want to have the water running for a minimum of 15 minutes. Increasing the speed of a full cycle to 30-40 minutes enables you to control the timing in increments of about 20-25 seconds.

      Nevertheless each enabled step amounts to 15 minutes of watering per day of course…

      1. I bought 2 timers last X mass for 12 bucks with a 12$ rebate, you can set them in a 15 min resolution, each one of those stops is 15 min.

        so if you need 30 min 3 times a day, just set 2 nubs where you want them, problem solved

        other timers are even better cause they are not on a fixed resolution, you can set them to 12.8 min if you really sit down and fiddle with it…

        now more on the point these things loose time like mad, you can sync them one night and they will be a handful of min apart 12 hours later. so its not like your getting something even remotely reliable int the first place

      2. Dude, what if you want one minute out of every seven or three minutes out of every fifteen? The only off-the-shelf solutions are cycle timers that run about $150 a piece. Hydro/aeroponics and mushroom cultivation are both applications that require this level of fine tuning.

  3. zrzzz, try looking for advice on what grow lamps you should get for any plant other than pot. It’s impossible; I gave up. I wanted to keep my tropicals from losing most of their leaves during the winter without having to drag them out every day and put them back in for the freezing nights (I live in the South, days below freezing are very rare). Still no idea what the best way to do it would be, other than to tear down the workshop I store them in and put a greenhouse in its place).

  4. I work with a company that manufactures this type of product.

    Unfortunately, it may not last that long the materials of the cogs are chosen for a 24 hour cycle the material may wear far too quickly and jam, not to mention the silicon based crease my not be upto the job of lubrication,

    But good luck on keeping it running.

    1. Dear Bob from the mail room,

      Thanks for your concern about the life expectancy of our ‘cogs’ (called gears since they are no longer made of wood). Had we known that you enjoyed giving off-the-cuff advice on the Internet in your spare time, we would have pointed out the following facts to you:

      All of the gears are made of the same tough self-lubricating plastic. Most of the gears – all the fastest ones – are traveling at exactly the same speed before and after the conversion*, and their lifespan is likely to be unchanged.

      In the future please check with management before discouraging potential customers from buying our low-cost, well-made products for any reason.

      *Unapproved tampering voids warrantee, but is otherwise none of our concern.

      CEO, Cheap and Reliable Timers Inc.

  5. i use hyrdo for my vegatable wink wink lol
    and i also have the ruuning pumping its only the light i have on a cycle,i perfer old fashioned feeding so i can keep a eye on things but this would be good to have a setup so you just leave it and come back,however i have seen ways of doing this rather than modding the timer

  6. A hack would be modifying this device to do something it was never meant to do, such as slapping rabbits. In this case, he simply made minor modifications to the internal mechanism and changed the period of the mechanism…. I’ll call this a “mod” at best…

    Damn stoners :P

  7. I just did this mod. I didn’t feel like going to ebay to get that stupid triangular driver, so I made one out of a metal rod using a dremel. It worked well enough, but I replaced the screws with regular phillips ones when I reassembled.

  8. Just finished making the timer. Very clever and quite easy once you have all the tools. The only difficulty I had was snapping the casing together after I had assembled the gears together. The metal motor arms were overlapping outside the casing. I eventually had to take the metal arms out of the motor casing and reposition them. Eventually it all snapped into place. Some hints for the then next set of builders. This is especially true for Canadians since we do not have such a good supply chain for parts. I bought two Westeck 2-outlet (could not purchase the 1-outlet in Canada) TM09DHB timers via for $30 including taxes and free shipping. The timers arrived in Victoria, BC from Ontario in three days. The screw driver needed is a tri-wing 2.0mm. I could not find it in any store in Victoria. I tried Canadian Tire, Home Depot, Home Hardware and The Source. You can buy it on the Internet for as little as $2.50 plus $6.00 shipping but that is in the states only. Shipping to Canada is exorbitant. I could find no Canadian Internet suppliers. They may be out there but I gave up because a techy person at work had a professional driver set from weitus tool of China. He let me borrow his. The 5/32 inch washers I got from Home Depot Canada for 46c each. They had a tray of about 300 of them. Likewise, it was really difficult to find this washer elsewhere. Follow Colt’s very clear instructions and there is not a lot to go wrong. My timer switches on and off every 36 to 48 seconds between pins. I guess that has to do with the gearing. I am very happy that I don’t have to spend $90 on a more sophisticated timer. I will now use it in my new airoponic growing system to switch a pump on for 1 minute and off for 9 minutes. Thanks Colt and good luck to the rest of you, especially those in the great white north. Douglas Adams, Victoria, BC, Canada.

  9. Westec has changed the timer a little bit and this has made the hack a little easier. I wrote it up over here with pictures (fig website):

    The shaft doesn’t need to be trimmed when it is in this configuration and the wadher size is nit super criticsl as the shaft lines up the teo gearsbthat are being glued together. What this hack dies is reduce the gear reductions from 6 to 4 so the timer dial runs faster. Still lookingvfor the ideal cycle times for hydroponic cloning…

  10. I just did this mod. Looks like the last comment was early 2016. It’s true the timer is different now, and easier to mod. Basically you throw away the same gear as in the video. But now you just need a washer that will fill the gap between the top gear and the one just below it so they turn together. My gap was about 2. 8 mm. I sanded down a slightly taller rubber washer til I got the right height. Then I glued it to the lower, then upper gear. No need to cut the axle or sand anything. Works great! I appreciate the work of the OP! Thanks.

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