brokenstuff

had this idea for a tempature failsafe


an on board digital thermometer that would shut the motor down if the motor reached a certain temp

cardriverx

hmmm thats not a bad idea, how would it turn it off? block the fuel flow? also how bout it sends the motor temp to the raido so you can see how hot it is without haveing to use a temp gauge!

tamiya08

My Feedback: (10)

they have that, made by venom http://www.venom-racing.com/ called the smart temp fail safe

brokenstuff

that records the temp and has a built in fail safe

but doesnt shut the motor off if it overheats just if it loses signal

tamiya08

My Feedback: (10)

no you program it to your max temp you want the engine to reach, then if it reachs that temp it limits the throttle until the temp it brought down.

your not gonna find and something that will shut off you engine if it gets to hot.

Frost_

My Feedback: (1)

Off the top of my head, here are the two easy designs to carry forward for potential prototyping:

The only real difference in the two is the analog device device used for the actual measuring.

1. The cheapest and easiest of the analog devices would be a thermistor. This technology previously had a practical limit that was too low... some around 125-135F, but it has been 4-5 years since I have done any thermistor component research. Their usefulness may have expanded, but 350F or so is almost certainly still out of the question.

2. The most realistic device (obviously any bi-metal devices, like the coil in your home thermostat, are out of the question because they need to be kept still) would have to be one of the several types of thermocouples. This is the snag. Thermocouple material is expensive and this sensor would most likely render your device cost-prohibitive from a production standpoint. To do this for your own use is the nature of a hobby though.

(possibly)3. Research may show that another analog option exisits (who is still useful, but I can't remember right now...)

EDIT 4. BEST OPTION. IR detection... you can get get the output you need... it may have to be clocked and a DAC used (or perhaps a fat digital input, such a micro may be more expensive than advised below)

Once you get your analog device, the heart of the circuit would be the microcontroller. The PIC micros can be purchased (applicable units) for around 4-5 dollars. Using the BASIC compiler the code would be a snap to write. You need to figure out the scaling of your analog measuring device and devise a suitable setup that gets your value into the range needed for an analog input to your micro. An additional analog input should be used for a potentiometer. This can be used to set the cutoff point of the engine at a certain temp; it would have a range, but not full scale (not say, 0-350... more like 290-300). The micro can be clocked at it's lowest setting. This reduces current consumption. The micro checks the analog maybe 20 times a second. Once the limit set by the potentiometer is reached, we have the micro set a digital output high. That high output will forward bias a cheap, common switching transistor transistor such as the 2N222 which will drive a larger transistor like a FET. This FET (protected by a diode from field collapse in the coil) will turn off or on a solenoid (NO/NC?). A tiny, affordable industrial solenoid can be used to cut off the flow of fuel to the engine. This circuit will require a few various resistors to help set biases and levels and possibly some caps for pins on the micro (cap-to-grnd).




That said, temperature tuning is something that I beligerently disagree with, and the device's cost would make it impossible to bring to market. Anyone with that kind of coin to drop into their nitro vehicle is not temperature tuning anyway. I just wanted to give you the best way that I know of to do it.

Frost_

My Feedback: (1)

Ha! I typed that while the link was going up! That unit could be modified to run that in-line solenoid I spoke of.... That is your best starting point from a hobbyist point of view.... just hope that it's temperature unit is more accurate than their P.O.S. on-board temp unit., which has been problematic for LOTS of people(1st hand!).

Jman44

Translated into english means...It would be too expensive or not possible with an afordable version. Or else you had better get that soldering iron heated up.