fan control with temperature influence on RPM

[NIbke]

Hi
I'm looking for a circuit that can do:
control the fan RPM by the temperature,but with some conditions.
If the temperature is below 40°C then the motor doesn't have to run.
It needs to vary in speed between 30°C and 70°C by RPM
And above 70­°C it needs to run at full speed.
The fan needs to run on 230VAC.
Ciruit input should also be 230VAC.
Does someone know where I can find somethimg similar?

 

[xnuke]

Why does it need to vary in speed between 30°C and 40°C if it isn't supposed to run below 40°C? Is one of these numbers a typo?

Sounds like you need a temperature sensor/transmitter combination that outputs a 4-20 mA signal over your desired temperature range and a variable speed drive controlled proportionately by that signal. (Some limitations may apply.)

xnuke

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[ozmosis]

NIbke
Firstly, I'm sort of assuming the fan is an industrial fan, not a domestic type.
I work for Siemens Building Technologies. We have a VSD/VFD called the SED2 that has a function called Hibernation mode. This operates whilst the drive is working in a closed loop PI(D) loop. Basically, you set a minimum level (and this can be degC)and when the temp drops below this point, the drive stops and awaits until the feedback temperature increases above a pre-determined restart temperature. This is automatic and requires no additional 'stop/start/input. We also have in the SED2 a direct input for a passive temperature sensor (internally we call it the ni1000). The ni1000 has a range between -50C to +150C and can be scaled within the drive. This can be used as your feedback device operating around a fixed (degC) setpoint.
The 230V range is 3-phase 230V in 3-Phase 230V out only though.
You can get info on:

http://www.sbt.siemens.com/HVP/Components/products/variablefrequencydrives/default.asp

 

[NIbke]

It needs to vary in speed between 30°C and 70°C by RPM
=>TYPO needs to be 40°C and 70°

For SED2 I think it will take abit to much room
the space I have is only 10cm high
And the fan is a regular tangential fan.
The purpose is in fact that It's need to be used in a fireplace.It should regulate the amount of air blown into the room depending on the temperature.
So it needs to regulate the fan between 40° and 70°
and above 70° it should turn at full speed.

 

[ozmosis]

I don't think it will be suitable. The SED2 is designed for industrial HVAC applications.
For your application you need to look carefully at the motor on the fan. As you want to vary the speed, you need a motor that is suitable for speed control and a 1-phase 230V motor is not that easy to control. On top of this you need a means of measuring the temperature and feeding back to some sort of controller that will in turn close the loop to your fan/motor. Sounds an expensive process methinks.

 

[Skogsgurra]

I think that your function is called "heat mover" by companies like PAX Electro Products. I am not sure about the temperature range though. Have a look at their home page

http://www.pax.se/eng_index.html

The 250 series is a "warm air transfer" fan that starts when temperature gets above the set point. Speed increases as temperature goes up. Perhaps you can scavenge it for the controller board...

 

[NIbke]

I found a schematic with very few components, just a 3 transistors and a NTC and a few resistors.
I just need to put it togheter.
I hope that will work.I just hope the thing doesn't get fried if the temp goes up to high.

 

[NIbke]

thx for the tip skogsgurra I'll take a look

 

[NIbke]

Sed2 developer I had another question for you about the drive.
For a certain project we do use drive controls.
And now I'am looking for a solution for controlling a motor through the PC.
For that project we have aour own program but is it possible to control the motor from our program.
Because I guess siemens will a have a program for conrtolling it.

 

[ozmosis]

It is not so much the program, more the protocol you would use between your PC and a drive. Siemens, and other makes of drives, supply pc based programs that can 'talk' to their drives. These generally use either proprietary protocols (i.e manufacturers own protocol) or can be used on open protocols (e.g. Profibus,LON, BACnet, Devicenet etc...). It depends on what you mean by 'controlling the drive'. What is your program based on?

 

[NIbke]

By controlling I mean regulate the frequency.
The program is written in C++.For the rest the program just collects data from a Daq card.

 

[OperaHouse]

Sounds like you are trying to control the speed of a shaded pole motor which you won't have too much luck with. If you can move up in size, variable speed ECM furnace blower motors are starting to be cheap. You would just have to put some electronics with them. You can also go back to a low voltage DC brush motor, maybe a car blower. I'm going to build a vaeiable speed control for my camper with about the same functionality. A TL494 from an old computer power supply, thermisistor, pot, and a couple of BUZ71 fets to drive the motor.