RPM Pulse Converter

[theboss85]

Hello Everyone,
I have a Comair fan with speed sensor output of +5VDC @ 2 Pulse per rev and I am trying to replace it with an alternate which has a speed sensor output of +72VDC @ 6 Pulse per rev. I need some kind of pulse converter in between to translate the signal. Can someone shed some light on this matter? It is not necessary to speed control the fans, we can have them running at full speed all the time. We only need to monitor the reported RPM.

Our quantity required is around 200pcs so this could be a paid job if someone can undertake it on turnkey basis.

 

[jpanhalt]

It's not clear to me whether you want to convert the 5 V to 72 V or the other way around. One way to do that shift is with an optoisolator (https://www.digikey.com/product-search/en/isolators/optoisolators-logic-output/3736381 ). Whichever way it is, at the 5V side you could use a divide by three logic counter. Here is one, about half way down the page: **broken link removed**

John

 

[theboss85]

Well I said I am replacing Comair with Ebm.
So the shift is from +72V 6P/Rev to +5V 2P/Rev

 

[jpanhalt]

Then put the optoisolator before the logic. If you are monitoring the speed with any sort of microcontroller, a big resistor and small change in code could also work. There is a very recent thread here on that approach. Here is the application note given by Eric: https://www.electro-tech-online.com/attachments/pictoac-pdf.82171/

John

 

[tunedwolf]

I'll go out on a limb here as you haven't given any model information, but the EBM TD series fans and quite a few others, generally use an open collector output with an external load resistor to interface to their respective speed controllers. You should simply be able to dimension the external load resistor to meet your existing 5v sensor supply. I would take care of the pulse count conversion using a small PIC micro to generate an acceptable pulse width for your existing controller. A bit more information would be helpful, like fan model information, existing speed controller etc

 

[mabell]

I am trying to replace it with an alternate which has a speed sensor output of +72VDC @ 6 Pulse per rev. I need some kind of pulse converter in between to translate the signal. Can someone shed some light on this matter?
www.rctopshop.com

 

[tunedwolf]

We can all make various suggestions, but unless you provide some more information it's not going to be easy to help you achieve your goal. At the least we need to know what fan model you currently have and what fan model you plan on upgrading to I did attempt to shed some light on the matter for you with my last post, not useful to you?

 

[alec_t]

You've told us the fan brands, but not the models.
What do the labels on the fans say?

 

[Reloadron]

I believe this link is a start to what is needed. This is why the exact fan model is required. If you are 100% sure about that pulse amplitude then something can be designed relatively simple. Knowing the exact model makes things go better, much better. Now if all you want is to take 72 volt pulses at 6 pulses per revolution and convert to what you had of 5 volt pulses at 2 per revolution then that is simple enough. However, if someone agrees to build 200 widgets to convert those numbers and it turns out the pulses aren't 72 volts then who has the problem?

Ron