Modernizing early 60's logic for paper tape punch - Page 1
Forum section: electronics / projects

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 25, 2016, 04:41:54 pm
content: Hi again! I'm sorry for my frequent thread-starting, but all my projects were just pushed aside by my newest acquisition: A 60's 8-hole paper tape punch!Now, this is a completely control-less unit. it has a motor, some coils to time the functions, and the punch solenoids, all fed out to a connector. Nothing more. The rest is in the electronic unit it is used with ( I don't have that).But all manuals, schematics are available, so it should be do-able to recreate that.Here's the deal: every thing is diodes and transistors. It'd take a massive amount of time and board space to recreate that, so I'm thinking of making an equivalent control circuit with a bit more modern parts, like TTL gates.Here's the logic overview schematic:It's not very recognizable, at least for me, and some logic elements are still unclear to me.- The "flip flop" used looks more like a SR latch. Some places with wired-OR inputs. The and/or gates are clear.- The "monostable multivibrator" element looks like something a 74123 could do.- The "differentiation of trailing and -leading edge" seems, mathematically, to must be some kind of positive/negative edge detector, giving a short pulse on rise/fall.-The "integrating" circuit, I have no clue, and I really hope someone might have seen similar in schematics.Here's the schematic of one of the data line latches:That's what I would try to avoid by using, primarily, 74-series TTL devices.Is there any device that looks to match the latch function in this system? I don't think there is a 74- or 40- series general SR latch.Of course the last stage will have to be TTL to *whatever* voltage a tape punch eats.Thanks for your time.--Christoffer

author: IanB
author_rank: Super Contributor
timestamp: April 25, 2016, 05:33:36 pm
content: Yes, I think the flip flop is the standard logic element of that name. If a pulse is applied to the "1" input it goes into the on state. If a pulse is applied to the "0" input it goes into the off state. It has "1" and "0" outputs which change according to the state.The monostable multivibrator is a timer. When a pulse is applied to the "1" input it turns on for a preset time and then turns off again.The differentiation of leading edge is a leading edge detector. When the input goes from off to on a short on pulse is generated at the output.I'm not sure about the integrating circuit. Maybe it is intended for switch de-bouncing somehow? It may turn messy transitions into clean on/off transitions.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 25, 2016, 07:25:26 pm
content: The edge trigger is somewhat in front of the monoflops or flip-flops.Modern monoflops are usually edge triggered anyway, and edge triggered flipflops are just D-flip flops.Simple SR flip flops can be made from 2 NAND gates like 7400, or a 7474 can be used as an SR flipflop, when ignoring the clock and D inputs.To me this looks like a job for a small µC, like a PIC16, 8051 or AVR.You might need this anyway to get the data from USB or at least RS232.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 25, 2016, 07:28:40 pm
content: That sounds reasonable. The integrator could just be a standard integrating amplifier, but I don't really see the use -exept debouncing, but why have that halfway between inputs and outputs?I'm also toying with the idea of just building it using standard pnp's and diodes, though it'll still take up a heap of space, the complete service manual would be golden for debugging/fault finding.This is the scale of the original electronic driver unit:QuoteI'd really like to keep it somewhat oldschool, and "dumb", but you're right, no doubt that'd be way easier.

author: Andy Watson
author_rank: Super Contributor
timestamp: April 25, 2016, 07:37:09 pm
content: In much that same way that the differentiator is detecting edges - I'm guessing that the integrator might be to remove glitches or other unintentional pulses (due, say, to a race hazard, etc.)

author: edavid
author_rank: Super Contributor
timestamp: April 25, 2016, 07:37:53 pm
content: Quote from: ChristofferB on April 25, 2016, 04:41:54 pmThey are probably just simple CR and RC circuits respectively.Quote74279CD4043CD4044Of course they don't save much over just using gates or flip flops.P.S. I would get it working with a microcontroller first, then convert to retro discrete logic later, if you still feel motivated. An Arduino plus a couple of ULN2003s should do it.

author: Pjotr
author_rank: Frequent Contributor
timestamp: April 25, 2016, 07:46:56 pm
content: Quote from: ChristofferB on April 25, 2016, 07:28:40 pmThe integrator thing looks something like a RC network generating a (pulse) delay. A RC followed by a schmitt trigger will do that.The original thing was for sure build using discrete components. Of course a MCU will solve everything but old school TTL looks more in accordance regarding its age.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 25, 2016, 08:23:07 pm
content: No doubt a microcontroller would be a good test, but I think I'll start by testing it completely dumb: apply power to the "run" solenoid (-17V) , some DIP switch combo of 8 bit to the (-16V, just for consistency) punch solenoids and then just run some test patterns.If one were to do it completely analog, since it's digital, it wouldn't hurt any to exchange transistors and diodes to 2n2906's and 1n4148's right?-No matter what course of action, I think I'll need to start with the super unintuitive power supply:Why bother running some solenoids at -17V and some at -16?

author: Macbeth
author_rank: Super Contributor
timestamp: April 25, 2016, 09:09:42 pm
content: It looks to me like it would be much more fun to implement using a cheap CPLD like an Altera EPM240 - that way you can draw all the logic gates and flip-flops up in Quartus to emulate the original and take it from there...

author: max_torque
author_rank: Super Contributor
timestamp: April 25, 2016, 09:45:58 pm
content: Use a CPLD or FPGA and see how fast you can run the tape!!#shredder

author: edavid
author_rank: Super Contributor
timestamp: April 25, 2016, 09:50:00 pm
content: Quote from: ChristofferB on April 25, 2016, 08:23:07 pmIt looks like the difference is not the voltage, but the extra filtering on the -16V. What's connected to that supply?

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 25, 2016, 10:26:31 pm
content: The -16v seem to only drive the feed solenoid (the one that allows forward tape movement). Dunno what makes that special from the rest.Man, finding that transformer will be tough. Might have to distribute it over several.QuoteHah! If it ever needs to die, that's the way to go.

author: Macbeth
author_rank: Super Contributor
timestamp: April 25, 2016, 10:39:39 pm
content: The -16 looks like it can deliver up to 2.5A with a filtered and fairly clean supply, while the -17 would appear to be supplying a more noisy and lower powered supply (being also tapped for the +/- 10V, etc)... Having a nice clean linear supply was quite expensive back in the day, so if you could chuck noisy crap voltages at circuits that don't demand regulation then go aheade.g. I have some lovely TIL311 hex digit displays that can have a crappy nominal 5V power supply for the LEDs while expecting a nice clean regulated 5V TTL for the logic. If you could afford to waste regulated supply on the LEDs then by all means, but the option is there...Without seeing the rest of the circuit though, who knows? Especially as there are no regulators shown the stated voltages are kind ofare they the open circuit voltages?

author: Macbeth
author_rank: Super Contributor
timestamp: April 25, 2016, 10:55:37 pm
content: Quote from: max_torque on April 25, 2016, 09:45:58 pmSeriously though, why bother with all that 74 TTL stuff when you can get an EPM240 breakout board for convenience and price from ebay or aliexpress for far less than the TTL chips. and the board is smaller. Perhaps replace the 50MHz crystal with something much slower to save on dividing it... (except for turbo paper tape punching overdrive mode) or just get a <$1 bottom of the range CPLD and design a board around it.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 25, 2016, 11:06:43 pm
content: Huh. That makes a lot of sense. I don't actually know if they're open circuit voltages, but they kinda look like voltages under load, don't they? Considering the drops from the transformer outputs to the voltage terminals.Here's the complete set of schematics (back of the manual):http://museum.informatik.uni-kl.de/Rechner/Zuse/Allgemeine%20Peripheriegeraete/Lochstreifen/Stanzer%20Facit%20PE%201500/Facit%20PE1500%20High%20Speed%20Tape%20Punch%20Manual.pdfIt bugs me that the logic has a +1V supply on some pins, but there's no 1V voltage output in the PSU schematic. Maybe it's just voltage divided down somewhere I haven't found yet..QuoteWell, I think my hobby in this area lies closer to "retrocomputing" than electronics. So my goal is to aim for what was accessible for a computer hobbyist back in the days. That's a challenge in itself, reading up on old magazines, finding projects and such, but furthermore I simply can't hold the interest when I get to modern microcontrollers, CPLDs and FPGAs.The nostalgia and charm dies completely, in my eyes, but that's just me being strange, I know.

author: Macbeth
author_rank: Super Contributor
timestamp: April 25, 2016, 11:30:28 pm
content: Horses for courses. I remember back in the '80s doing digital circuits all with TTL. Of course all the design was done pen and paper with logic gate stencils and boolean algebra. Then came the task of finding the TTL or CMOS chips needed and then finding Maplin didn't stock them or they cost too much. So making gates out of spare gates on other ICs would be the order of the day.I remember reading about these fantastical new devices - definitely not available to the hobbyist - ASIC's, GAL's, PLA's. Indeed the reason the Apple ][ was pirated so quickly is because they never had one of these devices that the BBC Micro or Spectrum had on board! Apple quickly learned how to be the ultimate in closed copyright retardation ever since...Anyway, I could only dream of drawing my logic design and making my own chip - in my own home lab!So my nostalgia is different, and though a microcontroller would actually be my easiest way of fixing this (I am more of a developer than an electronics guy at least for the past 20 years), being able to draw up some logic gates and burning them into a chip with no programming code whatsoever (VHDL, Verilog) is actually quite nostalgic!

author: moffy
author_rank: Super Contributor
timestamp: April 26, 2016, 12:31:28 am
content: I remember working with an 8 hole paper tape in the 80's for a defense contractor. All the code for their Inertial Navigation Systems was stored on paper tape before being loaded into ROMs, for nuclear EMP survivability. Each new code release was sent down from the programmers on paper tape which we then loaded into the ROMs. It was kinda funny at the time, reminded me of my university days and the stacks of cardboard cards we used for programming.

author: Macbeth
author_rank: Super Contributor
timestamp: April 26, 2016, 01:10:18 am
content: I also remember back in the late 80's our school computer dept. was donated an old school PDP/8 by some bearded engineer guy who was forced to get rid of it by his wife as it took up a whole room of the house. It was magnificent - the CPU board had thousands of pins all hand wire-wrapped - you could play it like a harp! Everything was gold plated. It came with a 640kb hard drive that weighed a ton and was the same size as a typical pedestal filing cabinet. It had two magnetic tapes on top and also came with four TTY serial VDU terminals. Oh, the 16kb core RAM pack expansion was something to behold as well! (IIRC it sat on top of the HDD cabinet).Now the thing is this beast had to be powered on all the time. If not then it lost everything. No DEC OS/8 or anything. It only had a front panel of switches and lights - all arranged in octal, not binary, hex, or decimal. I recall it was a 12 bit CPU as well - handy for that octal programming.So - with no OS or BIOS or anything we had to boot it bytypingmultiple switch levering in a fairly large sequence of octal code (that was conveniently pasted to the front panel). This code was just enough to enable the paper tape reader and carry on the process. All tape drives, HDD, VDU's were all dead at this point. That paper tape reader was a right bastard and we only had one rather worn out reel of paper tape with what I recall was the "RIM LOADER". It would often fail - then the PDP/8 required the reboot and the whole typing in all that octal using switches again...But it was amazing to see it when it booted into life - the reel to reel tapes would start spinning and actually loading DEC OS/8 - after a while, it knew how to deal with the massive 640K HDD and finally learn how to communicate with RS232 VT terminals which kicked into life with flashing cursor and the time shared OS.The paper tape loader was the achilles heel. We had to find a way of making a more reliable copy with a tape punch as a minimum - there was only one copy of this! But at the very least get it to run less erratically. I was anticipating fixing the damn thing, especially with the help of my more senior computer club friends...Actually it turned out the achilles heel was the Union Electrician Elfen Safety Nazi who came around and declared the whole machine a death trap to school children and it had to be scrapped. I think my computer teacher was actually quite glad as he didn't put up a fight and managed to flog it for all the gold and scrap value and pocketed a pretty penny for it. I think it was a crime, especially considering the benefactor gave it away for nothing thinking it would do some good.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 26, 2016, 03:29:55 pm
content: Amazingly sad to see a thing like that go. Completely worth the safety risk!On a last note, is the -16 and -17V so similar that you could use a common -17V supply, if you made it stable enough?Or maybe the brake solenoid puts such a load on it (it needs to hold back the motor) that it dips the supply enough to punch weakly?And how do you even make a 1V supply? just resistive-divide it out from one of the PSU's?

author: Macbeth
author_rank: Super Contributor
timestamp: April 26, 2016, 04:33:06 pm
content: I wouldn't be so sure it is actually -17V. The secondary is only 12V after all. Perhaps a slip of the pencil?

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 26, 2016, 05:35:19 pm
content: That's a very good point, how on earth would you get -17V DC from that arrangement? But it is labeled -17V all across the drawings, connector pinout inclusive.It's hard to test the voltage needed to a solenoid, I'd think It'd probably move at both 12 and 17V, just with less punch-force.

author: IanB
author_rank: Super Contributor
timestamp: April 26, 2016, 05:54:44 pm
content: Quote from: ChristofferB on April 26, 2016, 05:35:19 pm12 V AC rectified and smoothed would produce about 17 V DC. If the load is small enough that is what powered circuits would see.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 26, 2016, 06:01:03 pm
content: Well that's what I'm going with, then. We trust the manual, we trust the forum.Still think I'll split out into two transformers, with +-12 and +-19V respectively.And giant iron-core chokes. Looks like I'll have to find a HAMfest flea market soon.Thanks again for the advice.

author: Back2Volts
author_rank: Unknown
timestamp: April 26, 2016, 10:02:31 pm
content: During the second half of the 70s I was part of the software development team for the automation of a cold rolling steel mill. There were half a dozen Westinghouse computers. One of them had a fixed heads, 1MB disk, with assembler and Fortran compile/linkedit capabilities. It had a card reader and paper tape punch for objects and binaries. The tapes were then taken to the other computers and loaded to absolute memory locations using a 250 cps "high speed" tape reader. The computer I worked on, a 128KB memory-only system had over 4K control input/output signals, digital and analog. I put seven years of my life in that system.Tony -- Those were really other times and, yes, I am that old!

author: Macbeth
author_rank: Super Contributor
timestamp: April 26, 2016, 11:06:50 pm
content: My only other foray into paper tape was with a GE1050 NC controller for a huge 20 tool carousel vertical milling machine.Those tapes were not actually paper but some kind of plastic because in a machining environment they would be splattered with solly oil, swarf, dirty fingerprints and god knows what else. I learned all about G-code then and even though not a mechanical engineer it took me no end of explaining to my boss why his circular machinings were coming out oval. He was convinced it was down to "backlash" on the beds leadscrews - but a CNC is an indexed system and backlash is irrelevant. He finally got it when he slowed down the machining process so the GE1050 could do the job without my bosses frenetic envisioned £££ output!!It just took so much longer to work out all those x/y sines and cosines so let the ancient GE1050 some breathing space!Of course we replaced the utterly useless for CNC punched tape reader with a "BTR" (behind tape reader) that was patched in to the punch tape optics and then had a seriously long RS232 lead going to the office for CAM g-code downloads. The BTR could hold much more code than the GE1050 and all those circle functions where redundant and replaced with pre-computed X/Y/Z moves.However, we could only download that g-code during brief periods of TIG welder inactivity... It really interfered with my RS232 and 10base-2 network of Amigas and a shitty Windows PC. It was a fun job but really didn't pay the bills...