Please advise a device to change a pulse to on/off signal

AnalogKid said:

What are the manufacturer and the part number for the fan?

Usually a 48V fan has a tach output limited to 12 V or 24 V peak, or an open collector output so you can set your own peak voltage. The tach signal comes from a Hall Effect magnetic field sensor near the motor's rotating magnets, and is good for only around 10 mA. If the tach pulses really are 48 V peak, that is not a problem, just something to address in the circuit. Also, there usually are an even number of pulses per revolution. Are you sure about three?

What kind of "on/off" signal do you need? Does it have to be isolated from the fan power, or have to deliver very much current, or light an LED, or what?

This can monitor one to three fans:
https://controlresources.com/tachscan-3/

This monitors one fan per board. You can snap off as many as you need:
https://controlresources.com/tachstrip/

Note that both of those boards are limited to a maximum of 24 V power and 24 V input pulses.

Please ignore Colin's "advice". Simply attaching a relay coil to a power supply will do nothing to monitor the frequency of a low-energy pulsing signal.

ak

Click to expand...

AnalogKid said:

What are the manufacturer and the part number for the fan?

Usually a 48V fan has a tach output limited to 12 V or 24 V peak, or an open collector output so you can set your own peak voltage. The tach signal comes from a Hall Effect magnetic field sensor near the motor's rotating magnets, and is good for only around 10 mA. If the tach pulses really are 48 V peak, that is not a problem, just something to address in the circuit. Also, there usually are an even number of pulses per revolution. Are you sure about three?

What kind of "on/off" signal do you need? Does it have to be isolated from the fan power, or have to deliver very much current, or light an LED, or what?

This can monitor one to three fans:
https://controlresources.com/tachscan-3/

This monitors one fan per board. You can snap off as many as you need:
https://controlresources.com/tachstrip/

Note that both of those boards are limited to a maximum of 24 V power and 24 V input pulses.

Please ignore Colin's "advice". Simply attaching a relay coil to a power supply will do nothing to monitor the frequency of a low-energy pulsing signal.

ak

Click to expand...

AnalogKid said:

Nice fan. I've used EBM fans, although not this particular one; solid performers.

The tach output is open collector. The 47 V zener is there to protect the internal output transistor, and does not mean that the tach pulses must be 47 V in amplitude. So now it is back to you - what does the fan alarm circuit output drive, and what voltages are available to power it?

If the only power available is 48 V, then a 3-terminal regulator like the LM317 can drop that down to 24 V to power a Control Resources monitor board. That would then produce a 24 V output signal. If you don't want to build a regulator module, there are many small assemblies and kits to choose from.

ak

Click to expand...