What would you reccomend for building Sensing unit to increase fan speed for power vent blower motor?

Answer 1

You need to put more information here.... just what is it you are trying to sense? Where is the fan located? What are you trying to vent? These may all affect what kind of sensing unit you place on it.

Addendum: ok, its been almost 24 hours and the asker has not provided any more information.... I'll take a stab at a couple of options here, but without more information, it's just guesswork at what the asker is actually trying to do. Each scenario tho, the FAN is the critical element.... as to whether it is a multispeed fan or not. If it is not a multispeed fan, then this is all pointless.

First scenario: Let's assume this fan is supposed to help exhaust hot air, automatically.... like a powered attic vent (you find these on some mobile homes). In cases like this, there is a thermo-switch that will activate once the temperature reaches a certain point. These thermo-switches come in different ranges... can be bought right off the shelf of any industrial parts catalog. By using two (or more) thermo-switches of differing temperature range, and wiring them to the multi-speed switches on the fan, and setting them in the circuit so that they interrupt the the lower speed circuit when closing the higher speed... then you can cause a fan to go from "slow" speed, to a faster speed, once the temperature has reached the point that it will trip the higher ranged sensing thermo-switch. These switches are only a few bucks, and you could arrange a series of them, to match whatever speeds you have available on your fan motor.

Second Scenario: Lets assume you need to vent some kind of "fumes", whatever they may be. In this case you can use the standard chemical air samplers, and connect them to a small pc board that will monitor the amounts, and then tell the fan what speed to run at.... this kind of gadget can be bought off the shelf at Radio Shack, and is programmable for a number of various uses.

This same type of gadget can actually be adapted to many different scenarios, and sensing apparatus... your imagination is your only limit.

I hope this gives the asker some idea of how to go about what is needed, but without more information, there's not a whole lot of "specific" help I can give, like "which" sensors to use, etc.

I would recommend browsing Radio Shack's catalogs, and perhaps some of the large industrial suppliers like Graingers, to get more ideas of what is possible.

Good Luck!

Answer 2

If you're talking about a thermostat, that will not change fan speed. I'ts either on or off at it's predetermined speed