Need help multiplying a frequency

[tewkes]

I've been asking Jaycar, Dick Smiths, Aus, USA & UK component retailers (only because of ease of contact) for help trying to quickly switch a signal.

The circuit in question has a metal sprocket that passes a magnet/sensor which sends a pulse that relates to a speed on a digital display. It currently runs from 0hz to about 1khz, i need to speed this up to about 1mhz although anywhere from 50khz to 2mhz will do.

I have 3 wires i have the choice of switching. Switching either one will create the desired effect. one is 10vdc, one is 0vdc/earth, one is 5vdc. I've tried switching between the wires but it has no effect. I can manually touch the wires but nowhere near fast enough.

I've tried using a 12vdc motor 2khz motor controler but beacuse it sends 12vdc as it's signal it doesn't work.

It seems the sensor only registers if the SIGNAL itself is open and shut. I have 12vdc power supply available or anything i can buy from an electronics shop.

I'm a sparky so i have some reasonable knowledge about electronics, but this is beyond my understanding.

I've spent hours looking up mosfet's, capacitors, diodes etc. Even though maybe converting the signal from dv to ac to give me the pulse i need but i've hit a brick wall.

Any advice would be greatly appreciated as it's driving me nuts lol. i don't know the current available to me but i'm guessing it's reasonlable as it's a large display it powers up.

If I can measure anything to help out, just ask me and i'll do it.

Thanks guys!!!!

Paul

 

[(*steve*)]

You're doing a lot of describing HOW and very little describing WHAT.

You have a metal sprocket that passes between a magnet and a detector (hall effect?) and you want to be able to run this faster?

What does the "switching between wires" stuff mean?

 

[tewkes]

explation

I have a machine at my factory the runs a bit with several teeth on it at a given rpm, there is also a sprocket that has several teeth that pass a sensor (with 3 wires going to a display, 10dvc, 0vdc and a signal return which voltage is induced i believe). i have changed the blade to one with a lot more teeth and increase the rpm drastically due to cutting different material. I now need to speed up the display to show the correct rpm. I was thinking a frequency multiplier would do the trick but need a lil help designing one.

 

[(*steve*)]

So the RPM has increased, but the display of RPM is not changed?

For example it used to say 100 to 100 RPM and the RPM was 100 to 100. Now it still shows 100 to 1000, but the change in gearing (?) means that the speed now varies from (say) 500 to 5000 RPM. And you want to make the meter show the new speeds?

Or is the problem different to this?

 

[tewkes]

Correct

No, you are right! Any ideas?

 

[(*steve*)]

The easiest way would seem to be a table on paper. If you want X RPM, set to Y RPM.

It would be easy enough with a microcontroller to detect pulses arriving on one pin and generate some multiple of this number of pulses on another, but the counter itself may be limited in counting frequency.

You could also do it with discrete electronics (well, digital IC's) but it would be a lot more effort.

How much experience do you have with electronics and programming?

 

[nbw]

Yep, more detail would be good. Microcontrollers - even the BASIC embedded ones like PICAXEs - can easily count pulses of that order and are dead easy to use. Digital counters / dividers like 4040 and 4060 could help as well. Some of the CMOS variety will operate at up to a few MHz, beyond that the 74 hi-speed series come into play. Interested to hear more

Barney