EEVblog #962 - Hacking A Calculator Into A Counter - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: December 28, 2016, 02:44:22 am
content: How to hack a calculator into a test system event counter.

author: Mr.B
author_rank: Unknown
timestamp: December 28, 2016, 02:52:08 am
content: My, my... You have been busy today Dave.Thanks for that video. Nice simple hack to achieve the desired result.

author: Muttley Snickers
author_rank: Unknown
timestamp: December 28, 2016, 03:02:29 am
content: Nice enhancement.Unattended monitoring could be a trap for young conductors should the APO kick in.

author: rrinker
author_rank: Super Contributor
timestamp: December 28, 2016, 03:42:57 am
content: I remember doing that as a kid, adding an external contact to the = key. I had some big plan in mind but somewhere I lost interest and never finished. I don't THINK I got into any trouble - claculators weren't exactly a dime a dozen like they are these days, but I'm pretty sure we had 2 identical ones and I didn't touch the one that was most frequently used.

author: DTJ
author_rank: Super Contributor
timestamp: December 28, 2016, 03:59:54 am
content: This is a neat idea. I remember seeing it done in the 70's and used in conjunction with a astronomy telescope. Instead of adding '1' each time the contacts closed the fraction of a degree per rotation of the positioning lead screw was entered. Could be a useful hack for a cable reeling set up.One place I worked at we needed a quick and dirty field amphometer.We hacked transistors across the start and stop buttons of a cheap stopwatch and put together a circuit similar to the Electronics Australia (or ETI?) magazine 'Coax Sensor Amphometer".

author: MK14
author_rank: Super Contributor
timestamp: December 28, 2016, 04:05:51 am
content: I did similar, a long time ago, as a hobby project. If I remember right, I used a relay, so it could count any low frequency source that could drive the relay. You can also use a 4016/4066 cmos analogue multiplexer, may need a monostable (set to around 250 ms, else the calculator may not respond) as well. (CD4066B CMOS Quad Bilateral Switch).In theory you could use a transistor/mosfet. But it is tricky, because (as Dave says in the video), to get that to cope with the unknown multiplexing keyboard scan scheme.

author: smithnerd
author_rank: Regular Contributor
timestamp: December 28, 2016, 05:52:24 am
content: I recently needed to map out the keyboard matrix for the Chinese scientific calculators, which are currently available from poundshops here. The plastic/carbon keyboard membrane is glued on, so soldering to the PCB is completely destructive (but they are absurdly cheap). Pads are numbered left to right.

author: jonovid
author_rank: Super Contributor
timestamp: December 30, 2016, 09:36:37 am
content: as posted on your yt. IMO I would use hot glue to anchor wires in place. also I would use sockets as end connectors so you can close the back up.and re-use for other jobs in the lab.Chinese calculators & DMMs make cool loggers & hobby projects

author: Luminax
author_rank: Regular Contributor
timestamp: December 30, 2016, 12:02:14 pm
content: Hmmm.... I remember one of my old horizontal Casio can do a 0+1 and just press equals forever more and it'll add up. I forgot what the model is ... or if it's even really Casio or some Wun Hung Lo brand

author: AdiGital
author_rank: Contributor
timestamp: December 31, 2016, 09:15:06 pm
content: Hacking? A Calculator? Seriously?Dave! Please. I love watching your channel and learning from you but this is... just shocking. I'm sorry but it really is.

author: timb
author_rank: Super Contributor
timestamp: December 31, 2016, 11:08:44 pm
content: Quote from: AdiGital on December 31, 2016, 09:15:06 pmReally? Why?He needed a lap counter for the Batteroo train test. This was the quickest, easiest way to do it.Personally, I think it's super resourceful and very clever.

author: amspire
author_rank: Super Contributor
timestamp: December 31, 2016, 11:27:39 pm
content: Quote from: timb on December 31, 2016, 11:08:44 pmI agree. In terms of using something on hand that essentially has zero cost (people throw these things out), can run for hours and show up clearly on the single frame, it is a pretty brilliant solution. There is a better solution? Dave could have used his Agilent counter, but the calculator seems a better solution for the task. The counter display would not have been visible from the top down shot.

author: nctnico
author_rank: Super Contributor
timestamp: January 01, 2017, 12:05:00 am
content: Weirdest thing I hacked together with pushbuttons where pushbuttons attached to a cable to push buttons. That way there was some certainty that two systems where started at the same time without modifying one of the systems. Yeah, I once had a job where these kind of wacky ideas saved the day. I still kinda miss working there.

author: jonovid
author_rank: Super Contributor
timestamp: January 01, 2017, 01:30:47 am
content: QuoteI would do the same as Dave.but used maybe hot glue not tape.

author: AdiGital
author_rank: Contributor
timestamp: January 01, 2017, 12:22:17 pm
content: Quote from: timb on December 31, 2016, 11:08:44 pmI didn't want to be rude. Especially in my first post. I follow Dave's channel for a long time and I admire him and his work. I just couldn't believe he would actually invest the time and create an episode on exposing calculator's key. I'm not negating the idea and yes, this is the right and clever thing for the task. But even so, all I would expect (considering EEVBlog's high standard) was no more than a mention and seeing it in action rather than how to get the wires out.

author: VK3DRB
author_rank: Super Contributor
timestamp: January 01, 2017, 12:48:52 pm
content: I remember doing this is 1983 on a cheap 4 function calculator, except I had to do "+, 1, =" because it had no constant K function. One CMOS buffer IC and different RC time constants at the inputs would produce a round robin of key presses. It worked a treat and I thought it was clever because the circuit was so simple. If anyone is interested I'll see if I can find the circuit in my old filing cabinet and publish it here.

author: IanB
author_rank: Super Contributor
timestamp: January 01, 2017, 12:56:53 pm
content: Quote from: AdiGital on January 01, 2017, 12:22:17 pmBut why not? Not everyone who watches is an expert in everything electronic, and even a simple mod like that can stimulate thought about how to approach it and alternative ways of doing so.

author: SeanB
author_rank: Super Contributor
timestamp: January 01, 2017, 02:06:24 pm
content: Well, the calculator use has been around for a long time, at least since a calculator was available at such a low cost that you could think of them as something with a counter, display and a small controller you could buy for under $5. I remember appnotes that used them to make totaliser units, and even one using it as a postscaler for a faster counter, to improve resolution and give extra readout, at the expense of increased gate time. Another used a sequence of RC delays, like VK3DRB describes, to enter the startup keypresses on power on ( using a calculator that had no APO functionality of course) to make a "low cost robust totalising 8 digit counter for under $10" IIRC.The calculator provides really good keyboard debouncing, reliable counting and in this application, a perfect solution instead of ordering a counter that likely would never be used again much. Dave already has a plethora of cheap calculators, so just grabbing one, likely from the dumpster room as well, tossed out because they did not want to dust it ( yes it happens) is both cheap, efficient and a good solution to the problem.

author: jonovid
author_rank: Super Contributor
timestamp: January 01, 2017, 04:23:09 pm
content: QuoteYou cannot please everyoneif Dave had designed and built two identical dedicated pieces of batteriser testing lab equipment from the ground up with fabricated counter pcb's and crowdfunding of the cost. then had programmed all the counter logging software with a full color clock displays showing seconds plus cycle per lap, in real time milliamps voltage this requiring wireless data link modules if a moving toy is used in the testing. requiring a second power supply on the toy. had then setup two identical test rigs side by side. at the same time.maybe everyone will be happy.government departments work this way.

author: rrinker
author_rank: Super Contributor
timestamp: January 02, 2017, 01:13:40 am
content: Except Clive has stated several times that he just did that as a spoof. But it does prove what level your typical Internet user operates at - since THAT one went viral and got him name recognition. And as he explains on the recent questions and answers and rants video he mentions how he engaged a company to promote it and manage ad revenue, which he regrets, as they never pay, he had to sign over full rights to the video, and they do nothing to prevent the video getting ripped off - which he doesn't care about since he doesn't get money from that one anyway. It is in every way an atypical video for his channel.

author: jh15
author_rank: Frequent Contributor
timestamp: January 02, 2017, 04:59:55 am
content: Back in '81 or so we did mileage tracking for a bicycle club newsletter for brags 30 or 80 - 100 miles a day on weekends.A friend strapped a calculator to the rack a reed switch on the frame and a magnet on the spokes. exactly as as dave did. Owner happened to have a Honeywell computer in his basement and calculated wheel diameter etc. to get results.

author: rrinker
author_rank: Super Contributor
timestamp: January 02, 2017, 05:12:37 am
content: I remember building a (I'm pretty sure it was Radio Shack) bike speedometer that was pretty much exactly that - a magnet on the spokes and a reed switch. It used an analog meter movement, so I'm guessing it just displayed the average mv from a simple capacitor circuit where the cycle was started/stopped by the reed switch.As to Clive - I'm a rather obsessive person when I get my teeth in to an interesting topic. A bit over a year ago when I first found this forum, I watched a few of Dave's then-current videos, then I went back and started all the way back at the beginning and pretty much watched every single one in order. Pretty much the same with Clive although I did get bored with the multiple of the same sort of thing so I've skipped quite a few. That series he did with stuff from his day job was quite interesting to me.

author: SNGLinks
author_rank: Regular Contributor
timestamp: January 02, 2017, 09:19:00 am
content: What amazes me is that in December he posted a video a day apart from one day.

author: Wollvieh
author_rank: Contributor
timestamp: April 21, 2017, 11:46:39 pm
content: When I was a boy(which was aproximately about the same time as Dave) we had the same type of wooden toy train at the Kindy. Love it!But of course, no electric engine so shortly after the war.I learned about the idea of using a calculator as counter on a german TV DIY show, maybe around the early 80s: How to build your own step counter for walking and jogging. Just add some cable to the "="-Key and put a mercury switch in your shoe.

author: LarryStein
author_rank: Newbie
timestamp: May 14, 2018, 06:23:33 pm
content: Very nice idea. I just have 1 thought, why not use 1 - 1? It would allow you to start at the more convenient 0 point.Larry