Hi. I have an electric heated mattress pad that is controlled by a 0-10k ohm potentiometer. I would like to replace the pot with something I can control via software from an Arduino. I looked at several digital pot types, but from what I can tell, they all seem to be very limited in the amount of current that can flow through them. I also considered rigging up some standard resistors with relays, but that seems sort of ridiculous. I'll admit that I'm fairly weak on my analog electronics. Doors anyone have any suggestions for what I might be able to put in place of the pot?
I would steer away from modifying the heater controls as it's AC power and unless you have good knowledge and experience with household AC power there is a big safety flag waving here.
Actually, the unit is powered by a 16V 3.5A DC power supply. There's only DC running to both the control unit and the heating pad itself.
I haven't actually measured the current flowing through the pot yet, but I assume it will be somewhere around that 3.5A max when the heating pad is at maximum temperature.
ard00d:
Actually, the unit is powered by a 16V 3.5A DC power supply. There's only DC running to both the control unit and the heating pad itself.
I haven't actually measured the current flowing through the pot yet, but I assume it will be somewhere around that 3.5A max when the heating pad is at maximum temperature.
Okay. I don't really have a point of reference on that image, but this particular pot is about the size of 3 or 4 dimes stacked on top of each other. It's a Piher brand. On the side, it says "10k008m". I can't find any reference that helps with with that 008m might mean though.
I will try to measure the current flow through it later when I'm back at my work bench.
ard00d:
Okay. I don't really have a point of reference on that image, but this particular pot is about the size of 3 or 4 dimes stacked on top of each other. It's a Piher brand. On the side, it says "10k008m". I can't find any reference that helps with with that 008m might mean though.
I will try to measure the current flow through it later when I'm back at my work bench.
Most of us senior members here will be reluctant to overly support your modifications since the Arduino system was never intended or warranted for critical systems where human life could be harmed. There are all matter of laws that are violated when a commercial product is modified from as commercial/approved design. We are not shy, many of us would do the same as you and modify-that-sucker... But the difference is we would not put the modification out on a public forum. It is one thing if we cremate ourself, a totally unacceptable thing if we are involved in assisting you to inadvertently cremate yourself.
ard00d:
I haven't actually measured the current flowing through the pot yet, but I assume it will be somewhere around that 3.5A max when the heating pad is at maximum temperature.
I doubt that because the pot would get very hot and would be a hazard. More likely it controls a PWM duty cycle on a control chip.
Hi, can you post a picture off the controller where the pot is fitted and picture of the pot thanks.
It will save a thousand words with a couple of clear pics.
Now the bottom. You can probably zoom in and see the IC near the top, which is an LM2904. I cleaned up the other IC after taking the picture and it looks like a 16F684EA microcontroller. The pot is soldered through on this side at R133/R122 and what looks like "010" up from there. One of the other leads is on the same trace as the 010 pin. The remaining lead looks like it's connected to the same trace as the bottom/right of R202.
