I am currently building a digital tachometer with a pulse generator/signal generator (correct me?!) that is to measure the RPM of a 12v DC Motor, that rotates a blade through a sensor and is able to generate a digital output (high - low) signal that will go to the digital tachometer.
It is for a school project and am having considerable problems with it.
I have been able to construct the digital tachometer, power supply and mount and house the 12VDC motor quite easily but its just the sig.gen that has gotten me into alot of problems.
When the digital tacho is connected up to the output of a commercial sig.gen, with the increase in frequency of the sig.gen comes an increased RPM reading on the digital tacho. When connected to the output of MY Sig.gen, the reading on the tacho lasts for a small time then comes up with no reading.
The problem exists in the IR LED - Phototransistor, opto-coupler subsystem. I have tried various changes with the subsystem but hve not yet been able to rectify the problem. When I connected my sig.gen to the Oscilloscope, it seems that there is a change in amplitude but no change in frequency of the output signal.
So what can I do??
Also, some of these are various photo's taken throughout the journey. I intend to put a photointerrupter in tomorrow.
Thanks very much.
My teacher is a qualified Electrical engineer who retired from working
power stations so he hasn't really got a great deal of knowledge in the
electronics sector so your help is genuinely appreciated.
I have a phototransistor - IR LED opto-couple wired up in parallel so
to speak, in series with resistors. I have a horrible circuit drawing so
I'll try download a schematics program to help create a schematic.
I am putting this in tomorrow to test with:
**broken link removed**
Thanks very much.
My teacher is a qualified Electrical engineer who retired from working
power stations so he hasn't really got a great deal of knowledge in the
electronics sector so your help is genuinely appreciated.
I have a phototransistor - IR LED opto-couple wired up in parallel so
to speak, in series with resistors. I have a horrible circuit drawing so
I'll try download a schematics program to help create a schematic.
That's what I am trying to measure with the digital tacho...
I am really struggling with ideas on what to change now.
It could be rotating too fast at higher RPM's but even
when it is slower, there is no reading on the digital tachometer.
That's what I am trying to measure with the digital tacho...
I am really struggling with ideas on what to change now.
It could be rotating too fast at higher RPM's but even
when it is slower, there is no reading on the digital tachometer.
Ok. put on the drawing as much detail as required so that we can understand the circuit.
If your PC has a scanner, you could scan a hand drawn circuit.
If you have the Jaycar photo interrupter then I would try,
Connect the emitter of the photo transistor to ground.
Connect a 2.2k resistor from (pt) collector to 5V.
Connect a 1k (just in case) resistor from (pt) collector to pic pin.
Connect the LED to either 5V or 12V with a resistor to limit the current to 30mA.
Let us know how it goes.
Edit, from the data sheet. How do you know which pin is which?
If you have the Jaycar photo interrupter then I would try,
Connect the emitter of the photo transistor to ground.
Connect a 2.2k resistor from (pt) collector to 5V.
Connect a 1k (just in case) resistor from (pt) collector to pic pin.
Connect the LED to either 5V or 12V with a resistor to limit the current to 30mA.
Let us know how it goes.
Edit, from the data sheet. How do you know which pin is which?
Thanks heaps Mike but I'm going to be honest with you, what do you
mean by Pic pin? Also as you are aware, not the best data sheet.
When you receive the component however, the legs are the different
length and so I connected the collector to the positive rail and the emitter
to the negative... Is this correct?