Cold temperature protection circuit?

**The Grinch** · 07-28-2004, 04:28 PM

I'm trying to be a little proactive and plan for the colder months. I want to build some kind of protection to prevent my carputer from booting up in freezing weather. The short term idea is to build a master kill switch, but that's not enough. I would like to be able to tape a temperature sensor to the hard drive and have that run to a small circuit. If the temperature is below a certain threshold, it will cut the power to the computer or hard drive.

Does anyone want to attempt to tackle this idea? I don't know enough about electronics to design my own circuit, but I can solder like there's no tomorrow.

I'm sure that many people would find something like this useful.

**kneival** · 07-28-2004, 04:38 PM

Could you use a cold weather (house?) thermostat to make your power on button open circuit when the weather is cold?

**The Grinch** · 07-28-2004, 04:49 PM

Well, the cheap units have Mercury in them and rely on a level surface. A moving car would throw the mercury all over the place.

**owenjh** · 07-28-2004, 04:54 PM

you could get a microcontroller and a temperature sensor. and have some one write you some pic code to put on it to not give power when its under a certain temperature using a relay and then when an acceptable temperature is reached the microcontroller could then allow power to pass to the relay, it would probably be best if you didn't cut power to the hard drive, but to the whole system.

**brooksware2000** · 07-28-2004, 08:19 PM

Originally Posted by owenjh

you could get a microcontroller and a temperature sensor. and have some one write you some pic code to put on it to not give power when its under a certain temperature using a relay and then when an acceptable temperature is reached the microcontroller could then allow power to pass to the relay, it would probably be best if you didn't cut power to the hard drive, but to the whole system.

You are Correct in this idea. Maybe I'll tackle it after I finish reprogramming the ITPS. Very simple solution indeed. Will post back on this as soon as I have time to get to it. Damn good idea though (thankyou The Grinch and owenjh for the idea). I'm in the military in the Northern Tier area of the mid west and the temp gets colder here than in Alaska so a solution like this would be desireable to me as well. Maybe implement a small heater element of some kind to be turned on by the microcontroller to keep the system warm when it's cold out.

**MrSpace** · 07-28-2004, 08:44 PM

I think you'Re better having a switch so the sensor and controller be yourself.. way cheaper.

I'm also concerned since here in quebec when it's -30 outside and you car sits outside for 3 days, I wouldn't want either the computer or screen to start before the car's cabin get's hotter.

Etienne

**RX7FDTT** · 07-28-2004, 09:29 PM

Once you'd turn on the heater the switch would turn the pc on automatically... since the pc is setup to tunr on once ignition switch is tuned, which is something you could also wire into it...

There are several thermal industrial switches, I helped someone on the RX-7 forum find one, when he wanted to controll his ac, based on temps inside the car.... He had removed the manual controlls, and hard wired it to be just on... and said it was freezing

Here's the manufacturer
http://www.gaumer.com/ProductFilter....nwal17000therm

and here's the post
http://www.rx7club.com/showthread.ph...ght=Temp+Relay

**owenjh** · 07-28-2004, 10:43 PM

Originally Posted by MrSpace

I think you'Re better having a switch so the sensor and controller be yourself.. way cheaper.

I'm also concerned since here in quebec when it's -30 outside and you car sits outside for 3 days, I wouldn't want either the computer or screen to start before the car's cabin get's hotter.

Etienne

Depends what type of chip it is. If the chip is cheap these units could be cheap to make. Cost of a temperature sensor, cost of a microcontroller, cost of a relay, cost to make PCB, cost of some connectors + wire and a little time

Would it be possible to have some sort of way of changing how hot / how cold the 12v gets cut off by using some type of trimmer (radio shack Catalog #: 271-280)? One for hot and one for cold. Im not very good at electronics, but this is something I would be interested in implementing and working on as a project.

this may be a little off topic here but if I buy a basic stamp kit (parralax) will I be able to program cheaper chips or do I have to buy a basic stamp for every seperate project. I basically want 1 stamp that I can use to test / debug code, and then once I have finaly finished I want to be able to write that code to a chip that can only be written to it. Any help would be apprecheated here :-P thanks in advance.

**brooksware2000** · 07-28-2004, 11:09 PM

Yep, if you buy a Basic Stamp you will need one for each separate project. It's good for development then you can move it over to something more permanent that will be cheaper than the stamp. You can get PICs for like 1.00 or so. Also, you can use a trimmer to set the range of the temp detection. Go to parallax website and look at their application notes. There are plenty examples of using a basic stamp for thermostat type controls.

**owenjh** · 07-28-2004, 11:22 PM

How would I go about transfering it to a cheaper solution, I am interested in microcontrollers, but do not have the cash to buy one of the starter kits that I think will suit my needs. I can save up the money if I know that it will be useful in other projects by using a cheaper solution.. I know you can get the pics from rado shack for $1.89 i think, which is quite cheap, but do not know how to program them. I assume that they use a different language?