Project

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Buford
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Project

Post by Buford » Thu Jul 17, 2003 10:57 am

I wonder if someone would be interested in a little project I've been considering.
It involves temperature and time control of a low-voltage DC relay with 20A @ 120VAC DPDT contacts. I considered simply hard wiring a circuit using timer chips and related parts, but the multiple temp and time trigger points would make the design lend itself much more to a microcontroller-based scheme, and I don't have a micro lab.

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Bob Scott
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Re: Project

Post by Bob Scott » Thu Jul 17, 2003 11:34 am

Buford,<p>Could you please be more specific about the temperature and time control? Temperature of what? What temperature and why? Time control of what? Specific times or time periods and how long?<p>What is the coil voltage or make and model of the relay if you have already chosen a specific relay? <p>Bob :cool:
-=VA7KOR=- My solar system includes Pluto.

Buford
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Re: Project

Post by Buford » Thu Jul 17, 2003 11:40 am

Bob:
I didn't give all the specifics because I didn't what to take up that much space on the board. There are a couple of temp points (around 176F), and several timing cycles. Nothing too complicated, just details. I can email the full description to anyone interested.

larussell
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Re: Project

Post by larussell » Thu Jul 17, 2003 2:12 pm

I would do it with a Basic Stamp and a temperature sensor. You don't need a micro lab, just a PC and their cheapest getting started setup with the whole development environment right there on the chip/board that's going to be the final product.<p>You can do a discreet design with logic chips, etc, but it will be hard to change, and if you impute the cost of the design time at $50/hour, not to mention wiring and testing, it will be a lot more expensive.

ljbeng
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Re: Project

Post by ljbeng » Thu Jul 17, 2003 2:21 pm

Send me the details please. I have done a number of temperature related projects using PIC microprocessors. Thanks.<p>[email protected]

tcsserv
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Re: Project

Post by tcsserv » Thu Jul 31, 2003 2:01 pm

check at www.windmill.com for free software to load up on an old/windows driven pc you can use as your controller; uses parallel or serial ports for temp sensor input/output and controller outputs for switching. Many many apps and patches at their site.
Worth a check.

Will
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Re: Project

Post by Will » Fri Aug 01, 2003 9:27 am

An interesting project - It could be done with discrete circuitry but if, by specifying that the control device is a 20A 120 VAC (Contacts) relay and you envisage measuring temperature and then controlling heat output by varying the Mark Space ratio of the (ON/OFF) relay then then would be quite difficult to achieve. You would be much better off using a PIC. Dependent on how accurately you wish to control the temperature you might also have to consider use of an Integral style control term - which would be even more difficult with discrete ciruitry.
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