Is there any way to hack my electric oven's temperature settings?

I would love to use my electric oven for producing various kinds of dried food products: jerky, dehydrated fruit, etc. However all of these require being able to dry the food, meaning a temperature of 130-140° Fahrenheit; any hotter than that and you’re cooking the food, not drying it. Unfortunately someone somewhere decided that for “safety” reasons no electric oven sold in the United States should be capable of maintaining a steady temperature less than 170°. I’ve tried every trick I can think of: no, leaving the door cracked open does not produce a controllable temperature; and setting the oven to run cooler just changes the thermostat/display setting, with a true temperature of 170° still inviolable. Could a service repairperson get at and hack the code controlling this unwanted feature?

No, no repair guy is going to be able to do that. Some ovens have an electronic temperature calibration, but that only allows for ±35°F or so.
If you were really serious, adding a digital proportional (PID) control to the oven wouldn’t be very hard.

I’m not sure how the lower 170 degrees limit was determined but I’ve had two wall ovens (from different manufacturers, Electrolux and Bosch), both of which had warm (as a warming tray from 140 to 180 degress). The current one even has a proof setting that runs between 100 and 120 degrees.

So I’m not sure that the 170 degree thing is a federal law or something. Maybe all of the cook cycles need to be 170 for food safety, but if you have a separate cycle for warm or proof, that’s ok to drop below 170.

Ok, it’s possible. One method is you can hack your thermocouple. Usually these are differential circuits that ultimately measure a simple voltage. If you were to reverse engineer your thermocouple circuit, and solder to your oven’s control board a circuit able to make a fake voltage - like an arduino with a temperature probe and a DAC rigged up by filtering PWM to DC - you could do it.

Exactly what you’d have to do “depends”, it depends on the design of the temperature measurement on your oven.

Or a food dehydrator is $37 on Amazon. Cheaper than all but the shonkiest electronics you might solder to your oven’s controls, and much safer. It’s pretty hard to reverse engineer something without having it powered up and probing the board, and the 220 volt power supply to your oven will be somewhere in there, possibly on the same circuit board.

Not to mention you may not have an oscilloscope or soldering iron handy…

I’m not an electrician but wouldn’t an old style oven be comprised of a rheostat and a heating element run off 220? couldn’t you just run it off 110 by cutting off one of the lines? I’m not suggesting this be done but just throwing it out for those with the background to answer.

You might be able to use one of these Johnson Controls. Homebrewers use them to keep a refrigerator warmer than it wants to be at its coldest setting; you may be able to use it to keep a stove colder than it wants to be.

However, the former homebrewer in me wants to point out that making jerky at temps below 170 is probably not awesome. Dried figs, sure. e Coli, not so much.

Old-style ovens had a bi-metallic thermostat or something likei it to control a relay. Those could be easily adjusted, but modern ovens are microprocessor controlled, and so more complicated.

Just get a dedicated dehydrator. It’s much safer and you’ll get more consistent results.

better tell this guy.

the whole point of drying meat as a way to preserve it is reducing the water activity low enough where bacteria can’t thrive. the salt in the cure/brine just helps that.

If I interpret the action of that gadget correctly, it cycles the power line when the temperature changes. Assuming it is a single-throw type switch, if spliced into the freezer power line, when the inside temp drops, the power is cut off.

That’s the exact opposite of what the OP wants for his oven. The power should go ON when the temp drops. The gadget’s internal switch would have to be double-throw to work that way.

Also, the voltage would be wrong for the US. AFAIK, most consumer stoves use 240VAC, freezers use 120.

The Easy Solution

Why are you driving yourself crazy?! For thirty-five bucks this provides the solution to your problem, and it got 4 or 5 stars from 27 out of 31 reviews.

Indeed. Another factor is food dehydrators provide heat and airflow. Even if you find a way to hack your oven it just provides the heat it won’t flow warm air over the food being dehydrated. So it won’t even work as well as the inexpensive appliances purpose built for this.

The solutions in this thread remind me of when Mrs. Charming and Rested asked for an alarm clock that would wake her up by playing a certain song every morning. I have no idea, but my first thought was to buy the MP3, get a Raspberry Pi, some speakers, a power source, and an old-fashioned wooden radio to house it. With 50 hours of building and programming, I’d have exactly what she was looking for. Or I could buy this one for $27. Guess what I did?

Nothing. She didn’t really want the clock after all.

FWIW, my oven has a “warm” setting that goes down to 140 F I believe (can’t check it right now because of the PGE outage) and a “dehydrate” setting that goes down to 100 F. It’s a convection oven so it runs the fan when on dehydrate. I usually dry my jerky at about 105.

I discovered accidentally that when I turn on the oven light and close the door, it eventually warms up to about 125. This might do for drying if you left it a long enough time.

I never understood (and still don’t really) why every oven I use doesn’t allow a setting below 170.

I suspect that is because the heating coil is big (designed for heat loss at ~400 F) and a simple on-off control doesn’t work.

During my grad-school work, we had to design a batch reactor that would follow a simple temperature trajectory. Using just a on-off control proved to be bad because the thermocouple doesn’t really “catch”the average temperature in the reactor . We ended up using a SCR to control the heater coil and a PI controller.
Think about this way, the heater coil has it’s own mass (thermal inertia) and the thermocouple is a few inches away from it. So the thermocouple senses 120F and turns the power off to the heating coil. But the coil is still at 600+ degrees and the residual heat energy heats the oven internals much higher than 120F. This is also because heat loss from the oven to the surroundings is low at a lower temperature setting.
At about 170F, the thermal heat from the heating coil (when just turned off) becomes approximately equal to the heat loss from the oven. So the residual heat in the coils does not significantly spike the temperature when off.
You can fix the problem by having variable power going to the heating Element. In this case for example, for a setting of 120F, the controller will give 100 % power at 80F, 50 % power at 100F and 20% above 110F and turn off at 120F. But this controller will increase the cost.
You can sort of feel this problem if someone asks you to drive your car at 2 mph.

Just get the damn dehydrator. I have a Nesco (not the same one linked, but the internals are similar). I believe the temperature setting MAXES OUT at 160F, so the oven is already inefficient and inferior.

Maybe storage space is an issue? They’re pretty bulky, and that’s the only reason to avoid one. Some of the square ones might be more compact and you can put stuff on top when you’re no using it.

I hope it was either “I Got You Babe” or “We’ve Only Just Begun.”

Yeah, at this point I guess that’s what I’ll default to. Just kinda’ makes a mockery of self-sufficiency.