Page 1 of 3 123 LastLast
Results 1 to 10 of 23

Thread: Electronic help needed

  1. #1
    Senior Member
    Join Date
    Jan 2012
    Location
    Buffalo, NY
    Posts
    2,628

    Electronic help needed

    Im having an issue with an electronic detector on one of my printing presses and wanted to see if I could get a little troubleshooting help. No diagram unfortunately. My technician wants to get new sensors which it may need but i want to make sure theyre getting power. The new parts are about $750 and are in Japan. I dont want to buy them if theyre not needed, plus weeks of potentially wasted downtime. I dont know how to test them. Their function is to send and receive a beam through a sheet of paper as it passes between the sensor. It detects a double sheet by means of the expected density, presumably as a function of voltage. Once it has detected a sheet it sends its signal to the circuit board which will then determine pass/fail. It then sends the info downstream to other parts of the press for other timing and mechanical purposes. Without this information, the press will not function at all.20161229_101533.jpg

    20161229_101741.jpg

    20161229_101941.jpg

    20161229_101956.jpg
    The 3-wire cable is for the sender (lower) and the 2-wire goes to the receiver (upper).
    The receiver mount has been cracked for some time but broke when i took it apart. The receiver is still sealed and wires are intact.


    If ive been too vague or mre info is needed, please let me know.

    Pete

  2. #2
    Senior Member r4z0r7o3's Avatar
    Join Date
    Jul 2015
    Location
    Raleigh, North Carolina
    Posts
    1,309
    W/o reverse-engineering the driving circuit / controller (which could/also have some fault), you'll need the specs / data-sheet for the two components. There are a few ways you could find it.

    Can you get any numbers or codes off of either part of the sender/receiver?

    Do you have an electrical drawing for the press itself which may list names/types of these components?

    Failing those, your other option is to google around for sensors that do the same job (digikey is a good place to look also). Look at the data-sheets for them and see if they have similar connections.

    -------------------

    Other options/ideas:

    It looks like there's a bank of LEDs on the board, but I can't tell from the traces if/any/which are connected to the sensor pins. If you can remove that board and find out, it could make your life a lot easier. I'm guessing the machine does some kind of power-on self-test. If there are LEDs connected to those sensors, their blinkie-state at power-up could give you clues if maybe the sensors are fine and the board's brain-box (or some other component) is shot.

    If you have a DMM, you may disconnect the sensors, and hook up onto the pins marked + and - (use a pair of those grabby-clips for multi-meter probes, they're only a few bucks). Then power up the machine or get it to run it's self-test. Watch your DMM to identify the supply voltage to the sensors (one at a time). Most likely, it's in the 3 - 5 volt range, but it could be anything, so best to measure. Knowing this, you can disconnect the units and power them externally.

    Old computer power-supplies can be used pretty easily to obtain clean DC power at -12, +12, 5, and 3.3 volts. There are two pins on the main PS plug you need to short to make it turn on (23 & 24 or something like that, google it).

    With the sensors running from external power, and covered up or in the dark, you can probe (in DC voltage or resistance modes only) between the "a" wire and + or - to while sticking paper between the sensors. With some trial/error you should be able to tell if the sensors are working and what kind of output signal is produced - most likely either a pair of voltages or resistances (depending on paper thickness).

    Though really, having the datasheet for the sensors or very similar types will save you a LOT of time guessing at what the output should be.

    Last-ditch idea: Go ask the question on an electronics-related forumn, like Adafruit's or EEVBlog's, or elsewhere. Generally there are plenty of people willing to help with these things and quite likely much more knowlegable than I. Make no mistake though, it's going to be a time investment, the extent of which may make you think twice about just ordering the replacement sensors and board. But the above should at least get you started
    "Things that are complex are not useful, things that are useful are simple."
    - Mikhail Kalashnikov

  3. #3
    Senior Member
    Join Date
    Mar 2014
    Location
    Charleston, West Virginia USA
    Posts
    597
    Just from the info you provided, it looks like the circuit board has an indicator LED that probably lights when a double sheet is detected. The pot labeled VR1 is likely the adjustment for sensitivity of the detector.
    Testing them should be as simple as lining the receiver and emitter up and putting a double sheet between them. The LD Detector LED should light.
    I think the receiver should be the one with three wires.
    Was the machine working before you dis-assemble the detector?

    Standard IR photo-detectors, photo-transistors usually run from $1 to $14 each piece from Mouser Electronics.
    Bones

  4. #4
    Senior Member r4z0r7o3's Avatar
    Join Date
    Jul 2015
    Location
    Raleigh, North Carolina
    Posts
    1,309
    Quote Originally Posted by FishbonzWVa View Post
    I think the receiver should be the one with three wires.
    I agree with that as well. If you can hunt down the datasheets, it'll go a long way to knowing for sure what's what and how it's suppose to be. Then after, if they are broken, you can get nearly matching parts from Mouser/DigiKey/Wherever pretty cheap. If you can get the board out, you can also confirm w/n the adjustment pot is inline with the sensor or totally unrelated. I'd def. make a witness mark on it before you go twiddling it at all.
    "Things that are complex are not useful, things that are useful are simple."
    - Mikhail Kalashnikov

  5. #5
    Senior Member
    Join Date
    Jan 2012
    Location
    Buffalo, NY
    Posts
    2,628
    @razor thank you very much for your response. It'll take a bit to digest your post but I will reply with comments, questions, and quite possibly, results.
    Yes Bonz that pot is for that purpose exactly. The press ran on Tuesday as normal, but failed to operate at startup on Wednesday . I was attempting to wiggle the alignment a bit and the epoxy'ed repair gave up. I've attempted to hold and align that thing seven-ways-till-Sunday to get a response with no luck. I can't image the alignment is that tight. I happened to have a Ryobi technician in that morning doing a PM on one of my other Ryobi presses and he advocated starting the troubleshooting by getting new sensors after fiddling with it himself. Unfortunately Ryobi's use of this type of sensor for double sheet detection was limited to a small range of serial numbers so none of my tech support has any great experience with them. As I mentioned and Razor alluded, I have no schematic nor any way of knowing what the voltages are supposed to be, but I'd like to know if there's any voltage going to them. I was making an educated guess at which was sender and which was receiver.
    As I indicated above I will read over Razors post, but without some guidance I'm a bit hesitant about probing with my meter.
    I will take another stab at alignment tomorrow just in case. The mounting was in fact compromised, but it was still pretty darned close.

    Thanks

    Pete

  6. #6
    Senior Member
    Join Date
    Mar 2014
    Location
    Charleston, West Virginia USA
    Posts
    597
    LED's are 3.8v normally. So the two wire should be in that range. If you have the voltage there it does not mean it's outputting light though.
    https://www.amazon.com/850-1550nm-In.../dp/B00FW85SVG

    The receiver has ( + a - ) with the ( a ) being the variable output.
    If you put your positive lead on that and negative to negative, watch the meter for change while you try to align the emitter.
    I've had detectors that could only be aligned with a meter.
    Bones

  7. #7
    Senior Member
    Join Date
    Mar 2014
    Location
    Charleston, West Virginia USA
    Posts
    597
    Use small paper clips to stick down into the connector as test extensions.
    Bones

  8. #8
    Senior Member r4z0r7o3's Avatar
    Join Date
    Jul 2015
    Location
    Raleigh, North Carolina
    Posts
    1,309
    Quote Originally Posted by FishbonzWVa View Post
    Use small paper clips to stick down into the connector as test extensions.
    The paper-clip thing works (try it), so does a small brad-nail or unbent staple. However, they can be a bit fiddly, and you'll want a solid connection to the pins that you can trust (no false readings). You also have to be very careful none of the paper-clips short to anything. It's unknown how much protection circuitry the board has, and I'm SURE a new board is way more expensive than the sensors.

    There's almost no harm possible when probing in voltage-mode with a DMM, even connected backwards. The worst you can do is short out two pins with one probe end. Second worst (or maybe first) is to try and probe some ridiculous voltage (many hundreds or thousands) - normally made obvious by the size of trace/wire and/or insulation thickness. Those little wires / traces on logic boards are nothing (voltage and current wise). Probe away!

    Adafruit sells these little spring-loaded grabby clips. Pick up a set of those and a pack of alligator wires. Chop one alligator end off and strip the insulation back 3/8" or so. Match up the minigrabbers and alligator-wire colors. Pull the tail-end off each mini-grabber, thread the wire through the hole, and solder onto the lug. Now you can safely grab those pins and connect/disconnect to your MM probes safely and positively.

    With some more hunting, you can probably find the cheap-chinese ready-made variety on Digikey, Mouser, Newark, or wherever. For electrics hacking, these are hands-down the most useful adapters in my box. I use them more frequently than my DMM even. Or you can sell them on Etsy or Ebay when you're done
    "Things that are complex are not useful, things that are useful are simple."
    - Mikhail Kalashnikov

  9. #9
    Senior Member
    Join Date
    Mar 2014
    Location
    Charleston, West Virginia USA
    Posts
    597
    +1 on the alligator clips.
    If you don't have them, wrap the paper clip tightly around the test lead and insert the other end into the connector, makes the meter hands free.
    I use to keep them with my DMM until I got a set of real accessories ($$$$$$).
    Bones

  10. #10
    Senior Member
    Join Date
    Jan 2012
    Location
    Buffalo, NY
    Posts
    2,628
    So my steps this morning will be to probe the sending 2-wire connector with the press under power while feeding sheets through. (Systems are interconnected so certain things have to be happening for others to work.) I have heavy guage stitcher wire (staple) that will insert into the back of the connectors. I should expect about 3VDC. If I get voltage then I'll probe the a and - whilst having an assistant vary the position of the receiver.

    On the receiving 3 wire connector, is the "+" the positive power to the receiving probe? If all is well with the board should I be getting a voltage reading while probing the + and - on that connector?

    Thanks again for your guidance.

    Pete

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •