Need some help identifying this LED Help Please.

[bigmark1972]

Pictured below is a PCB from a tool changer in one of our older cnc machines. One of the LED's has been damaged and I would like to replace it. Parts are hard to find for this older unit and if I can ID this LED it should be an easy fix.

It's a 3mm dia LED, the circuit board has IH T-D94V-0 Printed next to the other LED's. I am not sure if this is even relating to the type but it could help? I know the board itself is 24VDC, the LED's have a dome top and are clear. Any ideas on what I could use to fix this board would be appreciated.

Thanks

 

[MacGyverS2000]

I see no reason it has to be an exact replacement (i.e., no need for a part #)... find an LED of similar color and size and solder it in.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[itsmoked]

Totally agree with Dan. Find the same color and size solder it in and 'be happy'. Oh, use a diffused type so you have a nice indication.

This IS just for indicating correct??? If not then we need further discussion.

The writing is the UL stamp of the circuit board material, nothing to do with the LEDs.

http://dkc3.digikey.com/PDF/T073/P2326.pdf

Or look at Mouser.com as they won't screw you on minimum penalty.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[bigmark1972]

It shines through slots in a encoder disk to what I think are photo diodes on the other side.

Can I assume clear or white would work, I am not sure what the difference would be. I do see resistors on the PCB so guess I will try to use a voltmeter to determine the voltage needed.

The zero side of the 24vdc flows through a series of 5 resistors on the way to the led's. They are creme colored with yellow/purple/red (in that order left to right) color bands on them.

Thanks again.

 

[MacGyverS2000]

Similar colored LEDs are going to have roughly the same voltage drop (at least for what you're working on). If this is an encoder, though, are you sure they're not IR LEDs? Did you ever see light shining out of these?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[bigmark1972]

I am not sure of that but I can find out.
I have other machines like this, I will check if they are IR. The encoder portion is not visible during normal operation but I may be able to turn the lights out, remove a guard and take a look.

 

[Skogsgurra]

Yes. Most likely IR. Everyone used them for tool identification before RFID. The longer wavelength and the good sensitivity of the IR phototransistors are the reasons. More tolerant to cutting fluid and dirt in general. Buy an IR LED that has specifications not too good. They were not too good back in the eighties. (If that is the date of the machine). Buy better ones (more mW radiaton) if the machine is later than that. Not a car aligner by any chance?

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

You will not be able to see them. One exception. Video cameras can see them just fine. With it running you may be able to see the working IR LED in a movie camera viewfinder. I have used that method many times. It will be seen as a bright white light.

If that is an LED for a sensor it IS an IRLED for sure. All the useful sensors made are IR. This means you cannot see the light p e r i o d.

You could measure the voltage across the associated resistor and then reasonably infer the LED is working. You have about equal chances the sensor has died as the LED has died. And about a 30% chance the LED still draws normal current but isn't converting to IR light.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[bigmark1972]

Got it, I was intending to look and verify I could not see light, meaning it would be IR. I have other identical machines that are working. I know the led is not working because it got ripped out of the board and is no longer there, (see pic).

It is a 1984 brother CNC drill and tap model Tc-221. They have been really trouble free for the most part. A loose mount on the encoder assembly allowed the encoder disk to grab one of the led's right off of the PCB (it's destroyed). Everything else looks fine so I might as well try to replace it and cross my fingers.

 

[felixc]

Any digital camera with an LCD screen will also show you the output of an IR source. That's the quick method to see if that damn remote works or not.

 

[bigmark1972]

That is a good tip, I'll have to check that out.

 

[jimkirk]

Another handy gadget for detecting IR is a card containing a rare earth phosphor. Radio Shack used to sell them, but no longer.
Try

http://www.rayscience.com/infrared viewer card.htm

or

http://www.ahmsystems.com/component...acturer_id,0/option,com_virtuemart/Itemid,26/

(a couple I found by googling infrared indicator card.)

They're the size of a credit card, you sensitize them by exposure to light (sunlight or fluorescent light is best). The indicator typically then fluoresces orange in the presence of IR light.

 

[itsmoked]

I've used those many times, they work pretty well!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com