Hi All...
I have been googling and watching videos and such with very limited success.
Does anyone know what comes out of an electric blanket control unit and into the blanket? As near as I can tell it seems it's 24VDC, but is it PWM? Is it just 0 to 24 VDC? Does anyone know how much current is supplied? Does the blanket give feedback?
I plan to reverse engineer a controller but I'm hoping for a starting point.
Thanks!
Feel free to chip-in with any details you think we may require.
AWOL:
Feel free to chip-in with any details you think we may require.
Well I'm just looking to hack up a control for my blanket. Not sure what other details you are looking for?
Well I'm just looking to hack up a control for my blanket. Not sure what other details you are looking for?
(My emphasis) See reply #1
Electric blanket had many design and made, we do not know what type of your electric blanket is?
You have to give other details like spec? photo?
These are some of the design, it is not 24VDC, it is running of AC main
Every electric blanket I've seen runs of power line voltage (120VAC here in the U.S.) And, I think they are in the ballpark of 100 Watts (maybe between 100 & 200W).
Like almost every other heating/cooling device they cycle on & off (no PWM).
I plan to reverse engineer a controller but I'm hoping for a starting point.
How many wires go to the blanket? If there are only two, there's no feedback from the blanket. If there are 4 wires there may be a temperature sensor in the blanket. And if that's the case, I'd assume it's a thermistor because they are cheap and easy to use.
One controller I took apart many years ago (for a 2-wire blanket) had a little heating-resistor and a temperature sensor inside the controller. So... You were really controlling the temperature inside the controller box (and switching the blanket on & off at the same time. So for example, if the room is cold it takes a longer on-cycle to keep the inside of the controller box warm and the on-cycle for the blanket is longer too...
DVDdoug:
Every electric blanket I've seen runs of power line voltage (120VAC here in the U.S.) And, I think they are in the ballpark of 100 Watts (maybe between 100 & 200W).Like almost every other heating/cooling device they cycle on & off (no PWM).
That is PWM, just very slow 
(I use about a 3 second cycle time on the heater for my hummingbird feeders and adjust the on time as needed to hold the heat plate at a constant temperature - just a slower PWM than what most people think of.)
DVDdoug:
How many wires go to the blanket? If there are only two, there's no feedback from the blanket. If there are 4 wires there may be a temperature sensor in the blanket. And if that's the case, I'd assume it's a thermistor
Mine has 4 connections but t is feeding 2 overlapping loops
The blanket is a Biddford and wow, it never occurred to me hat an electric blanket would be driven from 120VAC directly!
FRYING TONIGHT. Maniacal laugh.
Cannot do Kenneth Williams voice in text though
gpsmikey:
That is PWM, just very slow
ON/OFF control with hysteresis thresholds is not the same thing as PWM.
Jiggy-Ninja:
ON/OFF control with hysteresis thresholds is not the same thing as PWM.
In the old days we had burst fire controllers, Zero crossing point detectors with a no of half or full cycles being passed.
Entirely appropriate for a resistive load , and i suspect this is how they work, not had a modern one apart though.
There were low voltage heating blankets available but the control box was rather large, very expensive and i suspect medical use.
It is forty years since I looked at one of those at my gran's house, and I think that was direct 240V ac with a thermostat. As in no external controller and some mechanism to adjust the thermostat.
I suggest that because it is an unwatched mains device with a person near to it, the electric blanket is not a safe choice for tinkering. In an overnight application draped over the (victim?), build quality is much more important than for a standalone device with a fuse such as a kettle or fan heater.
I think the K.W. sneer would go like
"fixing that rusty old electric blanket are we ? well careful you don't do someone a mischief with that"
