Anyone on here an Electronics Engineer ?

[Gadgeroonie]

got a question about recording an RPM through a USB port

please drop me a line

Edited by Gadgeroonie on Wednesday 16th June 12:56

[Daisy Duke]

Mike, you might want to remove your email address from that post, otherwise the spammers are going to have a field day.

[Adrian W]

Gadgeroonie said:

got a question about recording an RPM through a USB port

please drop me a line

Edited by Gadgeroonie on Wednesday 16th June 12:56

You would have to convert it into a recognisable format first, usb is meaningless, most output devices will be square wave and the counter will just pick up the edges.

[Gadgeroonie]

this will convert voltages so i can read them using software

http://www.velleman.eu/distributor/products/view/?...

i'm guessing i need a shaft encoder to output a voltage

or use one of these to convert the pulse to voltage

http://www.national.com/mpf/LM/LM2907.html#Overvie...

[Adrian W]

what are you trying to count?

[Gadgeroonie]

road speed and rpm

[dilbert]

Why USB?
You're making work for yourself if it's just a one off.
I'd suggest RS232.
I'd recommend Arduino.

[Gadgeroonie]

USB because most modern computers do not have a comms port

if i use the rs232 interface - will have to convert all signals rather than just output voltages and use an interface to convert them

do you know of an off ther shelf rs232 interface to read rpm/road speed/temperature etc ?

[dilbert]

Gadgeroonie said:

USB because most modern computers do not have a comms port

if i use the rs232 interface - will have to convert all signals rather than just output voltages and use an interface to convert them

do you know of an off ther shelf rs232 interface to read rpm/road speed/temperature etc ?

The Arduino has either USB or serial, although I think in all cases it is treated as a comm port (virtual comm port in the case of USB).

The Arduino, is a small micro on a board with many I/O pins PWM, Analogue and digital I/O. You can do allsorts with it, and it's dead cheap.

The benefit of serial over a raw USB link, is that you have no special driver software to consider. Most computers will treat a serial port, virtual or otherwise, as a native device, and you can stream whatever you want to it.

You can write software for the Arduino, which will count pulses, measure voltages, control motors, whatever.

http://www.coolcomponents.co.uk/catalog/product_in...

Edited by dilbert on Wednesday 16th June 15:26

[Gadgeroonie]

the Arduino looks pretty interesting

but i will have to learn a new programming interface, which i havn't got time or the inclanation to do

I would rather use vb or .net and interface using a dll. The velleman will let me interface directly to vb etc

will the arduino read an rpm direct from a magnetic sensor

[dilbert]

Gadgeroonie said:

the Arduino looks pretty interesting

but i will have to learn a new programming interface, which i havn't got time or the inclanation to do

I would rather use vb or .net and interface using a dll. The velleman will let me interface directly to vb etc

will the arduino read an rpm direct from a magnetic sensor

It depends on the magnetic sensor, but for just a little more money you can usually get magnetic pickups with a TTL output.

Probably more important is the frequency range of the pulse train that you have. Slow is no problem. Fast is more so. If it's fast you'll need a way to count the pulses in hardware. The Arduino probably has a pulse accumulator, which would make things easier. In the limit you're looking at analogue techniques that use F to V devices like those you've already shown.

My guess is that you probably won't need an F to V, but I don't know for sure, because I don't know what F will actually be. Nominally I'd say the boundary between fast and slow is about 1MHz but it depends entirely on the details so it could be more or less.

Also, I've recently come across an embedded controller that can be programmed in .NET That doesn't interest me, but if you seek I'm sure you will find.

Edited by dilbert on Wednesday 16th June 15:44

[Gadgeroonie]

Hi Dilbert

i am guessing the frequency will be less than 500

what is a TTL sensor

thanks for the help

Mike.

[dilbert]

Gadgeroonie said:

Hi Dilbert

i am guessing the frequency will be less than 500

what is a TTL sensor

thanks for the help

Mike.

I just checked out your website. I'm confused as to why you wouldn't know this stuff already.

A standard mag pickup, is just a coil on a iron pole piece. The toothed (ferrous) wheel flying past it, induces a current in the coil, due to the perturbations in the magnetic field. Perhaps like a linear dynamo. Certainly, if you put a current through the coil you could use it to move a small piece of metal to and fro near the coil. It's the same thing in reverse.

The trouble is that the signal from a standard pickup is very small, and it's a current, not a voltage.

The TTL output pickups, are more or less the same size, but you provide them with a power supply, and they convert that small current into a logic voltage level. They have a couple of transistors inside them, in addition to the coil and the iron pole piece. TTL is a standard logic family, which is very common and supported by most electronics, including the Arduino, and more than likely your Velleman USB board.

[2.5bluenob]

This thread looks like its writen in a foriegn language to me, 90% over my head

[Gadgeroonie]

yeah - its not really in the right place on the Noble forum

i'm building a custom Dyno for a special project

got the rpm pickup working fine with a transistor based crank sensor

had the thing rolling and working today

i've now got the write the software to get it all to work which will take some time !