Masters, I need your insights regarding this problem..
The project I'm working on involves 10 exhaust fans connected to an arduino.
I wish to detect the status of the exhaust fans, whether they are working, malfunctioning or turned off.
I'm planning to add a current sensor to determine if the exhaust fan has a supply.
Is there anymore cost effective yet efficient and automatic way of solving the problem?
Hi, so you want the arduino to monitor the fans.
What variables do you want to measure and what do you class as a fan failure.
Current will tell if overload, on or off.
Voltage will tell if on or off, or fan open circuit (Volts but No Current)
Air Flow will tell if broken blades, motor failure, no power, obstruction in air flow (cause overheating).
Just some thoughts..
Tom...... 
To measure the air speed, you could use a hot wire sensor.
PeterH:
To measure the air speed, you could use a "hot wire" sensor.
Actually, two thermistors on either side of a thin insulating wafer. The one facing the airstream is cooled more effectively. You need two to compensate for ambient temperature.
The thermistors are more sensitive than a wire, at less power consumed.
If it's an important reliability or safety issue then you should always measure/detect the most important parameter, air flow, directly.
Having been in field service many decades ago plugged/blocked air flow was one of the more common failure modes in systems, rather then electrical problems with the fan.
Thank you for your insights! I'm sorry for the very late reply.
Updates on the project
Suggestions?Hi, what are the specs on the fans, if they are brushless fans, the internal controller will go into current limit, so you may not see much of a current increase.
Have you measured the current with a DMM, to check the theory?
Hope this helps.
Tom......
arduinoTime:
- I'm also considering RPM measurement but I want the sensor to be easily placed (no object attached to the blade and sensors should only be on one side of the fan e.g. no point-to-point infrared ). I'm having a hard time on this one
You could color the center of the fan. Then you could check for the reflected light. I'd suggest a checkerboard pattern. 4 quarters, 2 white, 2 black. Kind of the way a line following robot does it. However, I am not sure if it's feasible speed-wise, never tried it. As to the current-TomGeorge is right. You need to check it using a multimeter first.
Sir TomGeorge, I'm using Sunon DP200A. Is it a brushless fan? I tried measuring the current using a multimeter but there's no difference when the fan is on and blocked. Should I put an amplifier?
arduinoTime:
Sir TomGeorge, I'm using Sunon DP200A. Is it a brushless fan? I tried measuring the current using a multimeter but there's no difference when the fan is on and blocked. Should I put an amplifier?
The circuitry inside limits the current, most likely. Or maybe it's your power supply. What are you powering it from?
If the 1st is the case, that means 2 things.
1) you can't protect it by shutting it off when it gets stuck
2) you probably don't need too
Sorry, missed the fact they are mains driven.
Hi, it looks like they are an induction drive, no electronics, they quote a 50Hz speed and a 60Hz speed so they are mains synchronous.
If stalled long enough they will heat up however.
Tom.....
Sirs, what do you think I should do if I want to detect fan malfunction using current sensor?
TomGeorge:
Hi, it looks like they are an induction drive, no electronics, they quote a 50Hz speed and a 60Hz speed so they are mains synchronous.
If stalled long enough they will heat up however.Tom.....
Could it be that the inductance of them is so high it doesn't get saturated on 50hz? Just putting that out there.
How big are the fans? At work we have large fans which use paddle switches inside to detect if there is air flow from the fan. Something similar could be used in a smaller fan if needed.
Sorry, sir zoomkat, but how can you use paddle switches in fan status detection? Could you give us a drawing? I kept on imagining putting the switch inside the fan and blades getting stuck in the switch.
arduinoTime:
Sorry, sir zoomkat, but how can you use paddle switches in fan status detection? Could you give us a drawing? I kept on imagining putting the switch inside the fan and blades getting stuck in the switch.
They are called air flow switches. The fan creates a positive air flow which blows against the paddle target of the micro-switch. If switch drops out then it's because there is no air flow. Much better then just monitoring fan motor current as a plugged fan inlet will result is over heating of the equipment even though the fan motor is spinning fine.
Below are some paddle flow switches. It can be as simple as a small piece of thick aluminum foil hanging vertically from a wire attached to an arduino. The bare end of another wire attached to the arduino is put just behind the piece of aluminum. Gently blow on the piece of aluminum and it pivots back touching the behind wire and the closed flow switch circuit is made.
google sail switch
Thank you ,sirs, for the replies!
Hmm, but it's a little bit pricey. Can I use this instead? Piezo Vibration Sensor - Large - SEN-09196 - SparkFun Electronics
