Need help wiring my new optical sensor

[John Carlsen]

Hey all. Just received a new Optek opb857 optical sensor kn the mail and need some help deciphering how to wire it. I would really like to continue using my calculator. It is a new printing adding machine with a really fast processor, so it never ghosts out, just the lever switch i have that starts to float around 1100 rpm. So, here is a link to my datasheet. www.optekinc.com/datasheets/opb857.pdf
any help that can be offered would be super helpful. Im assuming that i can just use the same input and common leads in the same place as my lever switch, but it's the third lead for "anode" that i need help with and i assume that is to power the thing. Theres only three leads: input, common, and anode. Please help as I'd love to start using it and making my machine much more quiet! Also, can it be in the open air, or does it need to be inside my machine where it is dark?

[David King]

Well it's an IR led that needs a supply of 1.7V and it consumes 20ma at that voltage. How do you want to power it? You could use a 3V button cell or 2 AA batteries or a 9V wall wart but you need to know what your input voltage is going to be and then you need to solve for the voltage drop at 20 ma and put the correct resistor to drop your DC voltage by that amount. There's a very simple LED voltage calculator here: LED Resistor Calculator
(there are dozens of other calculators on the web too)

If you don't have an understanding of basic electronics, best to let us know so we can give you what you need.

The collector part isn't my forté but I'm going to say that you'll have to build a switching circuit to get the calculator to work.
Think about getting yourself a real counter and save us all the trouble of thinking about it...

Regarding ambient light, no worries there -unless you live in a toaster oven. That's why they chose the Infra-Red led.

[John Carlsen]

Thanks for the info. Im a relative n00b when it comes to stuff like this, so as much as you can dumb it down would be great. I kinda figured that i would need to get a proper counter. The reason I like my calculator so muslch is because of the big blue lcd display that can be seen across the room! The only red lion counter that seems to be in my price range us the cub three and it looks awefully small and no bright display. I have $40 to spend on a counter and need it to have lit up numbers not just gray scale as i have poor eyesight with these things. Any suggestions you have would be much appreciated. Im assuming it's easier to get power to/from the sensor easier with the countwer?

[David King]

John, do you have an ebay account? If you do, that's the place to get a counter. You'll pay pennies on the dollar. The Durrant 1800 I got for $12 has nice, red digits and an autostop/ preset so you don't have to watch the numbers spin at all. We go through all this about 20 times a year on this board so you might take some time and read through solutions that have been posted already.

Think of the LED portion of your sensor as a little light bulb. It needs electrons flowing through it to emit light. The electrons have to come in and they need a way to go back out again or they won't flow. The LED has two wires, one for the + and one for the -.
Your sensor has 3 wires; brown, black and red. You want to run 3V+ (2 AA cells) into a 68 ohm, (1/4 or 1/8th watt resistor from radio shack) and from the other end of the resistor into the brown wire that goes to the LED's "Anode". The black wire is the common which goes back to your 3V supply negative terminal.

An on/off switch would also be useful to save the batteries when you aren't winding. 2 AA cells should last 3AH/20ma or about 150 hours of continuous operation. No switch = new cells every week. of course you can just pop a cell out of the holder to act as a switch. Radio Shack has the holders as well.

Olde school resistors are color-coded, here is a color-code chart:
http://www.elexp.com/tips/clr_code.gif

The RED wire is the one that goes to your counter along with another connected to the common (black).

When the LED light can shine on the phototransistor, the photo transistor turns on usually (-sometimes they turn off but you don't care) That lets electrons flow from the orange wire into the black wire or something like that. If you have a cheap volt meter, you can check that out.

Operation: You want a spinning disc, mounted on your winder shaft, with a window or notch in it that lets light through *about* 50% of the time, i.e. it goes 1/2 way around the disk. The edge of that disc needs to spin between the two little posts -but you knew that already...

[John Carlsen]

Hey guys, I really appreciate your help earlier about wiring up my optical switch. I just had a quick question: I found this Red Lion counter http://www.redlion.net/products/grou...docs/01001.pdf and wondered if it would work well with my Optek switch: http://www.optekinc.com/datasheets/opb857.pdf ?

Thanks to you all, I understand how the sensor works, but it seems that I still couldn't figure out how to wire it up. There was mentioned a resistor in line with one of the wires, but I don't really understand much of electronics, although I am trying to. Would you mind giving me a hand in figuring out exactly what I need and how to wire it?

[David King]

John, I can only help you with the supply side of your optical sensor. It needs 1.7V at 20mA to light up the infra red light emiting diode that tells the sensor whether something is passing through it or not. Your Red Lion counter has an auxiliary power supply to run your sensor, that supply according to the data sheet you referenced, gives you 12V at 100mA, more than enough to power the sensor, in fact way to much voltage, so we want to limit that voltage to a trickle by putting a resistor in the path. To determine the correct resistor to drop the voltage from 12V to 1.7V we use that little LED calculator link i posted above.
The calculator needs to know three things to solve for the forth, "Supply voltage" that's your 12v so you enter "12" in the first box. Next it wants to know the "Voltage drop across LED" We can look that up on the Optech data sheet and it says 1.7V so we type in 1.7 in the second box. Lastly it need to know "Desired LED Current" -we look that up on the Optech sheet and see that it's 20 mA so we type in 20 and hit the solve button to get a resistance of 560 Ohms. Run a lead from the Common of the Optech (Black) to the common of the Red Lion (pin 5). Run another lead from the +12V supply pin (Pin 4) of the Red lion to one end of the 560 Ohm resistor and the other end to the brown anode of the Optec led. That will power the led when the counter is turned on. The Collector of the Optech is the red wire and it need to go to the "count" (pin 6) of the Red Lion. That might just work just like that. If it doesn't, get back to us and we can figure out if you'll need a "pull-up" or "pull-down" resistor to get the counter working.

[John Carlsen]

Thank you so much David! That definitely gives me something to go on and work at now. Would a 1/4 watt 560k ohm resistor work or do i need to rethink the wattage? Also, will this givw me the counts per second that I may need? Up to like 2000? Again, im very grateful for all your help!

[David King]

John there are two max speeds it will count at depending which circuit you engage. High speed is 10kHz (x 60 means good up to 600,000 rpm) or 100 Hz is the low speed which will get you to 6000 RPM (at 50% duty cycle) which should be plenty. Duty cycle is determined by the length of the window you cut on your disc, if the window goes 1/2 way around that's 50 % duty cycle.

The low /high speed selection is switch #2 of the DIP switch block. You'll want a ball point pen or equivalent to push the switches around. It looks like you can select all the input parameters from the DIP switch so you can play with the other settings if you can't get the counter to respond to the sensor right away. You should keep S3 set to "High Bias" since your source is 12V not 5V.

Now on the photo-transistor end of your Optek you can run up to 30V from the collector-> emitter, but only 5V from emitter-> collector. You should have no trouble running the full 12V from Pin 4 of the counter to the Red wire (collector) on the Optek but I'm unclear after that whether the common (emitter) then goes to the counter (pin 6) or not. I don't think you would hurt anything trying that but I'd read through the instructions for the set up first and ask more questions. Joe G. should be able to clear this up...

If you ran the IR LED numbers on the calculator above you would see the power dissipation needed which is .204W so a 1/4W should be OK but they suggest you bulk that up to a .33W which really means a 1/2W (I've never seen a 1/3W resistor). You can double the wattage of the set-up by using two 1/4W resistors in parallel (side by side) which will cut the resistance by a factor of two so you need to start with two 1.2K resistors to get 600 Ohms. I really wouldn't worry about it myself.

[John Carlsen]

Now on the photo-transistor end of your Optek you can run up to 30V from the collector-> emitter, but only 5V from emitter-> collector. You should have no trouble running the full 12V from Pin 4 of the counter to the Red wire (collector) on the Optek but I'm unclear after that whether the common (emitter) then goes to the counter (pin 6) or not. I don't think you would hurt anything trying that but I'd read through the instructions for the set up first and ask more questions. Joe G. should be able to clear this up...

I suppose I'm just confused as to why I would want to try it from collector to emitter rather than the other way. Is there a benefit to one way over the other? I guess I just don't understand the option and why it works the way it does.

[David King]

The spec is printed to tell you what makes the smoke come out, not so that you'd actually use it that way.

[RedHouse]

John there are two max speeds it will count at depending which circuit you engage. High speed is 10kHz (x 60 means good up to 600,000 rpm) or 100 Hz is the low speed which will get you to 6000 RPM (at 50% duty cycle) which should be plenty. Duty cycle is determined by the length of the window you cut on your disc, if the window goes 1/2 way around that's 50 % duty cycle.

The low /high speed selection is switch #2 of the DIP switch block. You'll want a ball point pen or equivalent to push the switches around. It looks like you can select all the input parameters from the DIP switch so you can play with the other settings if you can't get the counter to respond to the sensor right away. You should keep S3 set to "High Bias" since your source is 12V not 5V.

Now on the photo-transistor end of your Optek you can run up to 30V from the collector-> emitter, but only 5V from emitter-> collector. You should have no trouble running the full 12V from Pin 4 of the counter to the Red wire (collector) on the Optek but I'm unclear after that whether the common (emitter) then goes to the counter (pin 6) or not. I don't think you would hurt anything trying that but I'd read through the instructions for the set up first and ask more questions. Joe G. should be able to clear this up...

If you ran the IR LED numbers on the calculator above you would see the power dissipation needed which is .204W so a 1/4W should be OK but they suggest you bulk that up to a .33W which really means a 1/2W (I've never seen a 1/3W resistor). You can double the wattage of the set-up by using two 1/4W resistors in parallel (side by side) which will cut the resistance by a factor of two so you need to start with two 1.2K resistors to get 600 Ohms. I really wouldn't worry about it myself.

Your analysis is more confusing than the situation requires.

The forward voltage of the LED isn't the parameter your concerned about, you just need to calculate a current limiting resistor, nuff said, the LED only really needs like 16mA to 20mA.

I used to have a PDF floating around here on how to connect the optec's to Red Lion counters, unfortunately my copy was lost it in a hard drive crash last summer, otherwise I would have posted it here.

I have emailed it to several folks on this forum, perhaps one will chime-in an email it to the OP so he can get hooked up.

The opto-transitor is employed as a pull-down in standard TTL fashion, emmitter is grounded, collector has a pull-up resistor, the Red lion counter is connected to the junction of the pull-up resistor and the collector, easy as that.

[David King]

Thanks for chiming in Brad. Unfortunately I'm afraid the TTL mention has left me in the pre-transistor dust. Perhaps you can just point to the relevant data in the data sheets and explain in English what John needs to connect to what to get this working. I'm afraid I gave it my best shoot-from-the-hip shot and made a mess of things. John I'll apologize for my haste and take my departure.

[RedHouse]

John, which red lion did you actually get?

The link for the data sheet you gave describes two modules APLT and PBLT, which did you buy?

Looking at the two data sheets, now you "could" hook it up other ways and I'm not interested in taking the time to explore all these iterations, the following quick diagram I made should get you going now.

The counter has capabilities for providing some of what you see in my diagram but you would need to be able to verify things that apparently are beyond your current pay grade. (just a joke there)

Anyway, using the diagram I provided you should be up-n-running right away, you may have to experiment with the S3 switch setting if you have any trouble counting. The terminal numbers are referencing the terminals on the APLT/PBLT counter module.

[John Carlsen]

Thanks for your help Brad. Unfortunately, ive just started learning about electrical circuitry, so im a little lost with your diagram. Am i correct in seeing that you are accounting for four leads coming off the sensor? Because mine only has three leads. And the counter model that i bought was the APLT model. I understand all of what you were saying in your post, but I still cant read diagrams all that well. Would you mind giving me a hand with that? Any other info you need about my counter can easily be provided so just let me know.

[Jazz P Bass]

Three wires is what I see.
The rectangle is the sensor package.
The dot above the + on the diode is the Brown wire. Solder a 550 ohm resistor on this wire.
The dot above the collector is the Red wire. Solder a 22K resistor on this wire.
Solder another red wire at the dot end of the resistor. This is the counter pulse. Connect it to Counter Terminal #6.
Connect (solder) the two unterminated ends of the resistors together.
This junction goes to Counter Terminal #4. The power Terminal.
The dot at the - end of the diode & the dot at the emitter are internally connected together.
This is the black wire. Common (ground). Connect it to Counter Terminal #5.