Help with barcode reader replacement parts - Page 1
Forum section: electronics / repair

author: Sharkclaw
author_rank: Newbie
timestamp: February 18, 2022, 11:50:25 pm
content: Good day to everyone.This is my very first post and i have a question about a barcode reader which i'm working on, i work on a amusement company called Recorcholis here in Mexico, and we have arcade machines that dispenses tickets after people play on them, and when they are done playing and got their tickets they go to a machine called "Ticket Eater" wich counts and destroy fisically the tickets.The tickets have a barcode on them wich is read by the machine to validate the autenticity of the ticket and it sends the count to the costumer's game card so they can exchange those points for prizes, the thing is that the machines are kind of old and they have a photodiode (it has no numbers, id or manufacturer on it) and two IR leds that reads de ticket's barcode, they last very few months before they have to be replaced, i reverse enginnered the pcb since we got no schematics or "Real" service manuals to identify or find a proper replacement for them, but i can't understand some parts of the diagram that came out of the reverse enginnering process (bad designed schematics done by me attached).When tickets pass trough the "ticket inlet" the motor gets activated (not shown on schematics) and the tickets travels trough the camera assembly wich consists in 2 IR leds, a lense and a square picece of metal with a line cutted in the center so it allows to pass the reflected ligth trough the lenses, to the square pice and finally to the photodiode behind all of that (photo attached), i checked with a cheap Wun Hung-Lo Factory osciloscope and i got some readings, the photo labeled 1 is when the ticket passes trough the lenses and the signal goes to an opamp but it has some kind of oscilator or something which i'm not able to identify it's propouse, and photo labeled 2 is the output to the cpu after passing trough the opamp weird configuration.What i don't get is that arrangement on the opamp and the input signal on the opamp is very different to the exit signal that goes to the cpu, and i would like that somebody can help me by pointing me what is that arrangement on the opamp and what is it doing on circuit that changes the output signal so much.Edited because: wrong link, now corrected.Uploaded here schematics and photos since the site won't allowed me to attach them for the size.https://drive.google.com/file/d/1Jzo1h65VNuhNTWonJK4NDx_FW3dO2FsJ/view?usp=sharingThanks for your time and cheers from Mexico!.

author: abdulbadii
author_rank: Frequent Contributor
timestamp: February 19, 2022, 12:15:11 am
content: Apologize...but first please understand, much better way is upload our pics on public image e.g. imgur, imgBB and then insert it into image insert[[img

author: thm_w
author_rank: Super Contributor
timestamp: February 19, 2022, 12:16:55 am
content: Similar type of product here with the same board and schematic (BCR1000):https://deltroniclabs.com/wp-content/uploads/2021/06/TT-2000-TT-4000-Users-Manual.pdfThe camera: OTBC-0140Optoswitch: VTR16D1HFor the optoswitches, minimum IFis listed as 20mA, max 40mA. It looks like they are running the VTRs right up close to 40mA.Is the 5V supply stable and in spec?For the OTBC they are running ~35mA, but I can't find a spec for those.Are you replacing the LEDs with discrete parts or replacing the whole module?

author: Sharkclaw
author_rank: Newbie
timestamp: February 19, 2022, 12:33:10 am
content: Quote from: thm_w on February 19, 2022, 12:16:55 am5V are ok, not much ripple and the barcode pcb won't read barcodes on any other machine, it works setting it to count holes instead of barcodes.I'm replacing the photodiode and the opamp since we cannot buy them locally, electronic houses here doesn't even have smd components let alone photodiodes (when i mention photodiode either they want to give me a phototransistor or a Ir led), you willl say just buy them online or digikey but company doesn't allow that. and i was looking on to whats to use to replace it (they are digging their own grave i know but they operate like that and won't even think on changing that policy)And the schematics for the BRC-1000 on the pdf doesn't match the real product, the values and conections to components are different in the brand new board than the schematics.And i wanted mostly to understand the arrangement of the opamp and that all series of diodes and capacitors since i can imagine it's an oscilator of some kind and it alters the input data of the photodiode and outputs a whole new data i guess mixed with the oscilation portion (my gess) of the circuit.

author: thm_w
author_rank: Super Contributor
timestamp: February 19, 2022, 02:02:03 am
content: Replacing photodiode and opamp, with what part numbers. Or are you saying replacing with parts you take off other old boards?Whats the designators (U1, Q1, etc.) of the parts that need replacement, if its always the same.

author: Sharkclaw
author_rank: Newbie
timestamp: February 19, 2022, 07:48:59 pm
content: Hi! thm_w.It will be replacing the photodiode, but since i don't know the specification i can't tell what kind of photodiode to stick in there, as i was telling you these photodiodes are black magic here where i live as well as SMD parts, all we get from sellers is trough hole ones, excluding online stores and big cities ofc.i was thinking about moding the circuit to make it work with a LDR since i have seen some that uses LDR instead of the photodiodes with very similar schematics of boards, and i did put one LDR in the device under test, but it didn't work, probably because of the needed sensibility that the photodiode provides.i have bought some photodiodes before from online sellers (takes from 1 to 4 weeks to deliver), similar to the ones that came with the barcode and also various different types but also they don't work on all of our known working machines, i even considered that these photodiodes may be custom made since no photodiodes that i buy works and if i exchange the diode from a working unit to the device under test it just works out of the box.The diodes, transistors, leds, opamp all of that i can buy it locally, the thing is the photo diode that either i buy it and doesn't work, or no electronic house have it.Cheers!

author: Sharkclaw
author_rank: Newbie
timestamp: February 19, 2022, 07:55:07 pm
content: Quote from: abdulbadii on February 19, 2022, 12:15:11 amHi abdulbadii.Yep i will try to learn these forums code to insert images, i have never uploaded a picture in a forum before using an external image host, all i ever did was to upload it as attachement.Thanks for the point there!

author: tooki
author_rank: Super Contributor
timestamp: February 19, 2022, 11:22:42 pm
content: Quote from: abdulbadii on February 19, 2022, 12:15:11 amNo no no! Uploading here is by FAR the preferred option, because public image hosts can and DO go offline (permanently, I mean!), leaving broken images all over the place. It's happened before and it will happen again.Quote from: Sharkclaw on February 19, 2022, 07:55:07 pmPlease ignore his bad advice and instead upload your images here. Shrink and crop if possible, spread the images across multiple replies if necessary.

author: tooki
author_rank: Super Contributor
timestamp: February 19, 2022, 11:35:09 pm
content: Quote from: Sharkclaw on February 18, 2022, 11:50:25 pmThe circuit might make more sense if you draw it in a non-crazy way. The way it's drawn now makes it way too hard to figure out. (The schematic doesn't need to match the physical layout: for example, with the op-amps, you should arrange it for signal flow, not by pin numbering.)

author: Sharkclaw
author_rank: Newbie
timestamp: February 20, 2022, 12:55:52 am
content: QuoteYes that's true, i made it in a hurry, didn't have time to build it to scale or paint it (haha love that joke), but joking aside, i practically never make schematics that will be one of the few i have ever done, i can understand them but to lay it it's an art of it's own, let alone pcb design.I did try various photodiodes but none have worked, and that lead me to think it may be a custom made one, but that sound way to much improbable due to prices and that the pcb is not really worth to be doing that.and the thing is that i haven't been able to find a single one that works on any other of my machines, only the ones that came with the pcb works

author: tooki
author_rank: Super Contributor
timestamp: February 20, 2022, 01:08:43 am
content: Here's a quick sketch of the op-amp section of the schematic in LTspice.You are right: the circuit doesn't make sense. Istronglysuspect you made some mistakes when reverse engineering the schematic. (And I might have made more in copying it, since it's so hard to read.) The diodes in the op-amp (U1B/C) feedback paths suggest peak-detection circuitry, and your finding of a mysterious oscillator reinforces this: that could be the signal that resets the peak detect capacitors.