Electronics > Beginners

.... hitting the fan

<< < (5/6) > >>

StillTrying:
Hasn't anyone done this simple viewing fan blades with a photo diode yet. ;)
A 2k2 to 5k6 across the PD and a LED torch works fine. :)

Circlotron:
Put a 10 ohm or therabouts resistor in series with the DC power lead and put your scope across the resistor and watch the rate the current gets chopped as the fan rotates. Could be 3, 4, or 6 times per revolution or similar.

Nominal Animal:
Most PC fans have a tach signal (yellow wire), that provides two pulses per revolution.

PerranOak:
Thank you everyone for all the replies. So, in order:

bdunham7 : I’m guessing it’s mains as it’s 50Hz. I really wanted to use the photodiode (PD) as I already have some.

soldar: the light I use is a bright LED torch. Initially, the “detector” was simply the PD connected to a battery with the scope attached! However, see below.

magic: The fan has four wires but I want to learn how to measure the speed myself first using the PD.

Brumby: you’re quite right! I did try it otherwise but similar results. However, I will do as you suggest in future.

Cubdriver: I can’t – there are no curtains in this room! It’s a long story about SWMBO, etc.

StillTrying: I tried and it was better but went with an amplifier circuit.

ledtester: thank you but I don’t have a phototransistor and wanted to use the PD.

wraper: see above.

janoc: interesting, I’ll keep that one in my back pocket.

Jwillis: cheers, I will save all that good advice for when things are running better.

Rick Law: wow mate! That’s fantastic! I’m gonna print it out and go through it once I’ve posted this reply!

ledtester: it’s from an old Dell and is made by: Minebea-Matsushita Motor Corp and is the: 3615KL-04W-B96. It’s 12V and says on it “2.50A” which I guess is maximum current. Photo attached – this is embarrassing, now you can see my “Heath Robinson” attempts(!) The breadboard near the fan is the PD and LM358 while the one behind is a simple 555 based PMW speed controller.

koloko: thanks but I really want to use the PD.

StillTrying: Ah, really? Just  the PD and a LED torch? I had, in the meantime, gone for an amplifier with an LM358 and the PD in photovoltaic mode. I think I’ll go back and try your way.
 
Circlotron: that is interesting – I’ll try that after.

Nominal Animal: I admit I did cheat and look at that but I want to come back to that, if I may.


I have a lot of work to do, thank you all very much.

StillTrying:
You won't get much output from the PD using that large diffuse side of the torch, you need a smaller intense beam to create sharper blade shadows on the PD. I used a beam torch similar to this.
https://www.ebay.co.uk/itm/Tactical-Outdoor-LED-T6-Lamp-Flashlight-Torch-50000LM-Zoomable-5-Modes-18650/173555276628

At about the same distances as your PD and torch it was quite easy to get a 0.35Vpp cog-tooth shaped waveform, fan had 7 blades.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod