IKA-TACH forum

[ross_valusoft]

Hello Ibrahim,

Interesting idea. How much current are you pushing through the emitter side of the sensor? Or another way ... what is the value of R8 in your circuit? I see that the performance in the Vishay datahseet talks of 50 milliamps. Is this what you are using also?

Best wishes,

Ross

[ikalogic]

Hello Ibrahim,

Interesting idea. How much current are you pushing through the emitter side of the sensor? Or another way ... what is the value of R8 in your circuit? I see that the performance in the Vishay datahseet talks of 50 milliamps. Is this what you are using also?

Best wishes,

Ross

Yup, i'm injecting 45mA via a 100 Ohm resistor but have been working with 60 ohm resistors as well without any issues (although it's not in the specs....)

[ross_valusoft]

Thanks.

[ross_valusoft]

Hello Ibrahim.

I have just noticed on the data sheet that the detector only produces 110 nanoamps current. This would mean that your R5 must be very large in value ... maybe 10 megohms to get enough voltage to be measured by the AVR's ADC. Then the ADC input impedance would load the signal. Did you find this? What value did you use for R5?

Thanks,

Ross

[ikalogic]

Impressive reverse engineering!

Yes, R5 is quite high, 1MOhm actually.

Again, i am impressed

Hello Ibrahim.

I have just noticed on the data sheet that the detector only produces 110 nanoamps current. This would mean that your R5 must be very large in value ... maybe 10 megohms to get enough voltage to be measured by the AVR's ADC. Then the ADC input impedance would load the signal. Did you find this? What value did you use for R5?

Thanks,

Ross

[ross_valusoft]

Reverse engineering? No ... simply understanding your design approach.

Cheers,

Ross

[zipdogso]

I only know basic electronics and know nothing about programmable chips.

I am doing a PC/TEC related project which I will put on a computer forum later this year (If I can finally build it !) and have a requirement to check the working of 2 circlation fans in a sealed case...it is not possible to observe them from outside.

I have puzzled how to do this, within my capabilites, for over a year...then I spotted the IKA-TACH.

I would be happy at assembling two of the "DIY" kits with the pre-programmed atmels but it would appear things need altering slightly.

1.) It would be powered by small PSU instead of batteries with the power turned on/off by relay controlled by a main power switch. I would leave the IKA-TECH power switch in the on position. - Easy, I can do that....

2.)There would be no need for the "display" button....would it possible to just bridge this ? The display would then just constantly update whilst powered ? Yes ? If you agree it will work then Easy i can do that.....

3.) I plan to mount the 2 displays directly one above the other at the front of the unit meaning 1 fan would be about 350mm - 400mm from the display the other fan would be further back about 750mm from the display.
Is it possible to mount the sensor on a seperate miniboard appropriately fixed to read the fan, with trailing wires to the correct connections on the main board ? bearing in mind the lengths I have stated.
I don't really want to use a diferent sensor and have to reprog the atmel, or will the resistance of the trailing wires screw it anyway ? If I can fit trailing wires then I can do that....

If it would work OK with these adjustments then I will be very happy indeed.

My final problem I dont see solving......but it is only cosmetic...

the 2 displays are mounted 1 above the other.
I am very happy to display IKA-TACH at the top of the top display but would prefer it not to appear on the lower one.
I trust this is an atmel programming job

[ross_valusoft]

Hello,

I am sure that Ibrahim will answer your specific questions ... I just wanted to warn you that this will probably not work as you wish.

The tachometer works by shining a pulsing beam of infrared light at the spinning object. It measures the received light during the pulse and when the pulse is missing. Both of these measurements must be "correct".

If you put two pulsing light sources inside a 1 metre box, each will also "see' the pulsing from the other's light beam. It is like the wife and the husband each pressing their own television remote control. Chaos and divorce are sure to follow very soon.

A solution could be to switch one tachometer on for its measurement, store and display the reading, then repeat for the other unit ... "repeat and rinse" as they say. Attempting to run both at the same time will end in tears.

Cheers,

Ross

[zipdogso]

well it might work.... the fans are either side of a partition. the air flow is "pushed" through with one fan then through a number of radiators then "pulled" by the other. To ensure air only goes through the fans there is a partition around the central radiator section. it can be arranged so the sensors cannot see each directly. Would it not work like that ?

[ross_valusoft]

If there is no possibility for the pulsing light to be detected on the other side ... yes it should work.

The rest I leave to Ibrahim.

Cheers,

Ross