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A bit of googling finds product code APS90 - an *official* external PSU for the HR92.
Didn't find any specs, though.
Wow, that is unusual. I wonder what the expected use case is ? Perhaps it does have a 5 volt to 3 volt regulator built in then. I'm not willing to try on mine without concrete details about the official adaptor though.
During the summer the HR92 motor won't be running but the electronics will still need some power, so it might be worth removing the batteries (or slipping a piece of paper under a contact). Has anyone measured the HR92 current consumption when the motor isn't running?
Last edited by DorrisMancer; 29 September 2018, 09:41 AM.
Reason: typo
During the summer the HR92 motor won't be running but the electronics will still need some power, so it might be worth removing the batteries (or slipping a piece of paper under a contact). Has anyone measured the HR92 current consumption when the motor isn't running?
The lowest I can measure when it's idle is 2.6mA. But that doesn't make sense because that's not nearly low enough to give a >1 year battery life with Alkaline batteries. 2.6mA would only give a life of about 3-6 months even if the motor was never used, so there must be some even lower standby mode to achieve that which wasn't entered in the time that I was testing. Perhaps the constantly changing measured temperature while holding it in my hand kept it awake and didn't allow it to fully sleep.
It seems to jump up to about 4.5mA for about a second every few minutes which I presume is the receiver coming on to receive the periodic update from the controller, and the backlight increases it to 7mA.
During the initial SYNC mode when it tries to establish a connection to the controller it consumes 25mA continuously until it makes a connection, which is presumably the transmitter. So HR92's that are in SYNC mode a lot due to losing connection with the controller are going to use a lot of battery!
The motor brings it up to 30-90mA depending on how much force the motor is exerting. 90mA is the highest I saw at any time.
Last edited by DBMandrake; 29 September 2018, 01:07 PM.
Lovely idea - slap a TEG on the radiator and keep the batteries charged. Only problem is what do you do on a cold day when the batteries are flat - you need a hot radiator to open the valve - but you can't get heat unless you can open the valve and there is no electricity...
Lovely idea - slap a TEG on the radiator and keep the batteries charged. Only problem is what do you do on a cold day when the batteries are flat - you need a hot radiator to open the valve - but you can't get heat unless you can open the valve and there is no electricity...
Obviously it would charge some rechargeable batteries with several months worth of battery life... such as the NiMH that are already supported by the HR92...
As long as the average power supplied by the peltier device was greater than the average power draw of the HR92 it would work. And if it's <2.6mA that is not much, even for a peltier device. And with all that hot surface available I don't see why it wouldn't work.
Two problems though:
1) Many radiators don't have a sufficiently large flat area to adhere a peltier device to, at least on the rear side, due to all the bumps and fins and you wouldn't want it on the front for appearance reasons.
2) The major problem though is what do you do with the cool side of the peltier device ? To generate power you need a heat sink to cool the cool side. Often that literally is just a stuck on heatsink. If the device was attached to the rear of a radiator in the gap to the wall this heatsink would have great difficulty in attaining a significantly lower temperature than the radiator side of the device - thus no power generated, as only a difference in temperature generates power.
On the front side of a radiator it could radiate IR into the room to cool itself so it would work a bit better but still be an eye sore. So in theory it could work but I suspect heatsinking of the cool side is the challenge, aside from adding cables and some gizmo stuck to your radiator. In the end changing batteries every 2 years is a lot easier!
A perhaps easier approach would be a very small solar panel. They will produce some output with indoor lighting and will receive some indirect daylight as well. This could be enough to average over 2.6mA but might still be an eye sore.
Seems like a lot of hassle (and additional ugliness) when changing a couple of AAs every two years is hardly a major chore or expense.
My thoughts exactly.
I guess the APS90 power supply is for commercial installations where they don't care about the ugliness of an extra wire and don't want to rely on someone being responsible for following up low battery alerts.
But how often is Evohome used in business or commercial installations I wonder ? It doesn't really seem it's intended market, unless we're talking about relatively small SOHO businesses with just a few rooms, community centres, those kind of places...
Obviously it would charge some rechargeable batteries with several months worth of battery life... such as the NiMH that are already supported by the HR92...
In the end changing batteries every 2 years is a lot easier!
Oh I agree entirely,it just seemed like such a fun idea. No doubt someone will develop something like it one day perhaps long thin devices that replace a fin which would provide the necessary cold sink? Until then I'll keep changing the batteries...
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