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Thread: What would you like to see in evohome? (have your say)

  1. #371
    Automated Home Legend
    Join Date
    Sep 2014


    Quote Originally Posted by gordonb3 View Post
    That's quite simple: it's V*I. The main question here is: how do the curves for `I` relate to each other when you feed the motor with 3V versus 2.3V?
    So do we know that the motor is normally driven at 3 volts ? Has anyone measured it ? In stroke 1 or stroke 0 mode ?

    There is a clearly audible difference in motor turning speed between the two stroke modes so the voltage must differ between the two. If we take 3 volts as the nominal voltage then 23% of the power supplied for the motor would be consumed by the diodes due to the 0.7v drop.

    This could have a significant effect on battery life, however the thing that is completely unknown (and which some of us have speculated about before) is what proportion of the total battery consumption of these units is the brief bursts of operating the motor and what proportion is the wireless comms and standby power of the circuitry... although the motor uses orders of magnitude more current when turning, it's duty cycle across a day is also vanishingly small.

  2. #372
    Automated Home Jr Member
    Join Date
    Oct 2016


    This is great! Going to give it a go. Thanks DIY1.

    Honeywell should be a little red faced if this works.

    I’ll let you know. (It won’t be anytime soon though).

    Quote Originally Posted by DIY2 View Post
    Like others I have noisy HR92s that I cant have in the bedrooms so I have done a quick hack that so far has solved the problem for me without any problems, so thought I would share it.

    The bad news is you need a soldering iron (but it’s an easy job).

    However do this at your own risk –and it will definitely invalidate any HR92 warranty.

    The design flaw is that the motors/gears turn unnecessarily fast and generate the noise. I have purchased alternatives from China and might give them a go at some point but in the meantime put in a hack that works for me.

    To slow the motors and reduce the noise I reduced the voltage to them - crudely using 2x 1N4001 diodes. (Zeners would be slightly better but I had these already and they worked fine). Note I have not done any voltage or current measurements to refine the diode selection – might do at some point.

    NOTE: in slowing the motors, the motor power will decrease, so if you have hard to operate valve pins this might not work –ie not enough power to operate them and the HR92 will show error E2. If this happens you could try different diodes with less voltage drop than the 1N4001, but less voltage drop equals faster motor equals more noise.

    This took me 15mins but may take up to half an hour of faffing first time. Lots of text for completeness but it’s a pretty easy DIY job.

    You will need:
    1. Soldering iron
    2. 2x Diodes -I used 1N4001 (12pk on ebay for £1)
    3. Insulation sleeve – again cheap on ebay
    4. Small jewellers type of screwdriver

    1. Remove HR92 Cap and batteries
    2. Remove plastic insert by removing the screw and using the small (jewellers) screwdriver bend the 3 retaining tabs GENTLY IN TURN while exerting slight lifting pressure on the insert (fingers in the battery compartment). Be careful not to over bend them or they will break, bend just enough so that they release in turn as you lift the insert gently. This sounds difficult but is actually easy if you take your time and be gentle.

    You will now see the motor.

    3. Unsolder the Red motor wire (doesn’t actually matter which one). Note the wire insulation is cheap stuff so melts easily, so don’t be too crude – you can re insulate with a sleeve if you melt it a bit.
    4. Take the two diodes and twist their legs to attach them in parallel together pointing in different directions, ie with the stripe on them at different ends – see picture (if you don’t you will get an E2 error from the HR92 as motor will only turn in 1 direction)
    5. Solder one end of the diode legs to the Red wire and the other to the motor. Use an insulation sleeve to avoid the diode legs shorting to the motor metal cover (and to cover any melted insulation on the Red wire). I don’t recommend using insulation tape – but hey it’s your HR92. Note: Its important to mount the diodes neatly – flat to the back of the motor and in a place that the plastic insert wont foul when you put it back on – I suggest place in the picture.
    6. Refit plastic insert – you may need to bend out one of the tabs again gently. Don’t force it down –if it doesn’t seat right its probably fouling on the diodes, so don’t force it and re-mount the diodes.
    7. Refit the insert screw, add the batteries and cap.
    Your ready to try it.
    Note if you do this to a spare HR92 and want to fit it to an existing zone –then follow the unbind procedure otherwise you will get a Comms fault on your controller – I just deleted the zone and added it again and hit bind on the modified HR92 to be sure.

    Attachment 1443

  3. #373
    Automated Home Jr Member
    Join Date
    Mar 2019


    Happy to help. Cheers.

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