Hello Guest it is May 13, 2021, 09:36:22 AM

Author Topic: testing a reflective object sensor??  (Read 7748 times)

0 Members and 1 Guest are viewing this topic.

testing a reflective object sensor??
« on: December 25, 2007, 01:20:06 PM »
Hello all and Merry Holiday.
I've been trying to hook up a spindle indexer to my lathe and I just cant seem to make it work so Ive decided that the first thing to do is to test the reflective object sensor Im using.
I figured an easy enough test would be to get a small 5volt ac adapter.
first I hooked the positive side of the power supply to the sensor and then attatched a voltmeter between the out put of the sensor and the negetive lead.
then I just pointed the sensor at the sun and watched the voltage jump to 5 vlots then covered it and watched it fall.
so far so good.
now I figured I could test the infer red emitter on the sensor by just conecting the pos and negative leads to the power supply and trying the same test in the dark with a reflective object (hense the reflective object sensing) anyhow I could not get this to function like I had thought. I cant get any voltage change.
I have 2 different sensors and Ive tested them both and cant get either of them to work. so I was curious if there is another way to test these sensors or if Im even doing it properly.
I understand that its an infrared emitter but should I be able to see any kind of light coming out of the emitter ( like old tv remotes) or would I not be able to see anything.
Im using this sensor
http://www.fairchildsemi.com/ds/QR%2FQRB1134.pdf
please help.

« Last Edit: December 25, 2007, 01:24:04 PM by guynamedbathgate »
Re: testing a reflective object sensor??
« Reply #1 on: December 25, 2007, 01:53:41 PM »
hmm Im wondering if I blew the LED. am I supposed to use a resistor on this thing to bring the current down or what? I guess trial and error isnt always the best way to go.
any info anyone can provide on hooking these things up would be appreciated.
If I wanted to use a external power supply to run the emmitter. what would be the proper way to hook it up.
again If anyone has any info I would love to hear it.
Chris

Offline Whacko

*
  •  239 239
  • Happy Days
    • View Profile
Re: testing a reflective object sensor??
« Reply #2 on: December 25, 2007, 02:44:53 PM »
Chris, check the emitter with your cell phone camera or a digital camera. The image sensors in these consumer goods detect the infrared spectrum. Go on, try it on your TV remote.

Whacko for invisible light
Nothing's impossible

Offline Whacko

*
  •  239 239
  • Happy Days
    • View Profile
Re: testing a reflective object sensor??
« Reply #3 on: December 25, 2007, 02:46:43 PM »
And yeah, you got to limit the current, somewhere between 25ma to 60ma

You blew it for sure

Whacko
Nothing's impossible

Offline Whacko

*
  •  239 239
  • Happy Days
    • View Profile
Re: testing a reflective object sensor??
« Reply #4 on: December 25, 2007, 02:48:09 PM »
You can always strip the one out of the TV remote. Just make sure you tuned the TV to your preference before you hack the remote! :)

Whacko the hacko
Nothing's impossible
Re: testing a reflective object sensor??
« Reply #5 on: December 26, 2007, 01:26:04 PM »
Ok well I ordered a new one . so Im doing my best to come up with what size resistor to put in line with this thing but Im having a bit of trouble. I'm ok at assembling electronic components but sizing them Im affraid is not my strong suit.
I have a little 5 VDC, 300 mA ac adapter I was planning to use to power this thing. what size resister should I use in the circuit to power the emitter?
Chris ???

Offline Hood

*
  •  25,838 25,838
  • Carnoustie, Scotland
    • View Profile
Re: testing a reflective object sensor??
« Reply #6 on: December 26, 2007, 02:49:50 PM »
I am crap with electronics but are you sure its AC volts you need? thought it would be DC.
Hood

Edit
Ignore me, I must have been seeing things, could have sworn I saw 5VacĀ  :o
Edit again
Ah I did in your first post, so I am not going totally mad :) so presume it is a 5V dc?
« Last Edit: December 26, 2007, 02:52:55 PM by Hood »
Re: testing a reflective object sensor??
« Reply #7 on: December 26, 2007, 03:05:30 PM »
yeah sorry about the cofusion. I just refer to AC to DC adapters as AC adapters . but I really mean. I'm using 5 volts DC. Guess if im gonna keep doing this I better get usedd to calling things by their real names.
Chris

Offline jimpinder

*
  •  1,232 1,232
  • Wakefield, West Yorks, UK
    • View Profile
Re: testing a reflective object sensor??
« Reply #8 on: December 27, 2007, 06:46:33 AM »
I am using the Fairchild sensor, looks like the same one.

If you look back in the posts, you will see a wiring digram for this. Basically the transmitter is wired to a 5 volt supply thorugh a current limiting resistor. This shines down and then reflects back to the receiver.

The diagram shown ( and I am very sorry, but I have forgotten who submitted it, although I enclose a copy here) shows on the input a pull up resistor. The inputs lines to the computer already have pull up resistors, and two proved too much, so I removed it and the sensor works very well. It is mounted above the lathe chuck mounting plate (which I painted matt black) the reflector was from my grand-daughters "stick on" shiny things, and I picked one that was like a small mirror (about 6mm by 6 mm).

I picked off the power supply from my stepper motor drive cards (24 volt) I used a 5 volt regulator on a small piece of circuit card. This is quite adequate and saves any other input to my box of tricks. The regulator runs up to 1 amp, so there is plenty in hand for other sensors or applications.

I found the sensor very sensitive to being the correct distance from the reflector (although if you study it you can see why) - it has to be at 90 o to the spindle, and the beam has to go down the transmitter, then bounce back up the receiver.
Once it is installed and working it is faultless. I have several others ( I think I got four) and I am thinking a replacing my limit/home switches with them, if I can figure out how to mounted them. I think they will be a lot less susceptible to swarf and other little metals which short the terminals of my micro switches.

Jim
Not me driving the engine - I'm better looking.
Re: testing a reflective object sensor??
« Reply #9 on: December 27, 2007, 07:56:34 AM »
thanks jim but I have already tied this circuit and have not been successful with it. I,m using Bob campbells breakout board so that could be part of the  problem. for its input terminal i has 3   screw terminals.

       1                   2                  3
  Ground              signal              12 VDC


I have not been able to make that circuit work for that board.
wich is why i decided to go with a seperate power supply for the emmiter. Ive been able to get the signal to the PC to work simply by hooking the the sensor to the signal and ground terminals and shining it at the sun to test it. My index light comes on as it should in Mach so I figure I should just power the emitter with a seperate power supply to save the trouble.
but again Im not sure what size resistor to use on the power supply to prevent blowing the LED again. so If anyone knows how I can achieve this I would be greatful.
again I have a small 5V DC power adapter that out puts 300mA. I figured I could just use it If I know what size resistor to put in front of the LED.

Chris
« Last Edit: December 27, 2007, 07:58:35 AM by guynamedbathgate »