EEVblog

How to hack a calculator into a test system event counter.
Previous video on contact debouncing and using a universal counter: • EEVblog #961 - Monkey ...
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[@zer0b0t]

Hacking anything, that's the kind of content I really like to see.

[@zer0b0t]

Ugh?

[@thelavian4481]

You often tell random people what to do?

[@arcade_signal]

I think he meant hacking in the original technical sense and not in the "soft" sense where the word has been co-opted by morons and applied to silly stuff. It's even been bitten by marketing people, search for "growth hacking" to discover a new and exciting world of idiots

[@electronicsNmore]

I did the same thing using one of those inexpensive tally counters. Worked great with the magnet and reed switch.

[@PiratCarribean]

I read "Hacking A Calculator Into A Calculator" 😂

[@NoxMarcus]

Dave is SO prepared to demolish the Batterizeroo. Got all the toys lined up, I love it. I don't care about the actual device itself. But all this stuff showing how to accurately disprove the b.s. is really interesting.

[@anotherdayisforever]

One of my favorite DIY vids youve ever done!

[@DoRC]

batterizer test setup!!

[@mbirth]

I somehow expected you to seamlessly implant a calculator into a counter top …

[@kryskarr23]

Cool tutorial. Big fan. Take care and keep up the quality work.

[@orvillejones1258]

Nice project Dave, thanks for sharing!

[@TechGuyCharlie]

Hi Dave, such a cool project there! Would have looked great with a VFD display calculator.

[@MyBigThing2010]

this is genius....I would never thought to do this on my own...I'm not that "creative" ...thanks for the idea, just saved me an eBay purchase, saved money and a month of time waiting for CE garbage to get here...all for the cost of a jst, a scrap of wire, solder dots and a few minutes of time! definitely gonna give this a go! THANKS AGAIN.

[@NicholasAarons]

That Was Awesome Dave. Keep up the great work. Nick.

[@BendeVette]

I used this when I was 18 (34 years ago) on my bicycle to count the distance of my trip. You could enter the circumference of the wheel and each rotation would add this to the previous result. Worked wonderfull. Magnet and a reed relay.

[@rogerkerr5745]

I saw this done by a couple of guys who wanted to count the number of turns when winding a motor. It was a brilliant simple hack which performed perfectly.

[@linengmiao]

More of such hacking video's please! It is a real pleasure to see you hacking/modifying and reverse engineering stuff (in stead of mostly just analyzing and explaining like we are used to).

[@nickhill9445]

Love the idea. Another possibility is to put the reed switch inside the calculator case. It can read the train directly without affecting the calculator appearance, and you can use a solenoid placed near the calculator for other applications.

[@TechsScience]

This videos deserves millions of views

[@umajunkcollector]

happy new year dave, good one Don

[@mooncabbagere]

This week on EEVBlog's The Dave Jones Show, Dave hacks a calculator to count automatically!

[@Blendedasian]

holey queen spikes, look at this fabulous smooth footage! Thanks, dave, you're making your videos way more pleasant to watch with 50fps. welcome to the pc master race club.

[@samgab]

PS, you can also hack a cheap pedometer to do the same thing as this. They just have a little weight and switch inside which increases the count by one ever time the weight moves and closes the contact. You just remove the weight and solder wires to the two contacts and then you can connect those wires to any switch, such as a reed switch and magnet or a light sensitive switch, etc.

[@mattshilling]

Samgab Better solution!!

[@rpc72]

Samgab was gonna post the same comment when i saw yours.

Great post Dave!

[@thevoid7480]

Forshadowing the batterizer test setup. ;) But why not use an arduino for that? You can collect and store the data and send it to a PC. Then you could also implement a timer that measures how much the train slows down instead of just counting loops. Collect more data!

[@tambechristian]

You are a genius Dave !!

[@ralfgottfridhansson3127]

Nice battery tester ! Happy new year!

[@andrewsalton7670]

simple,cheap and reliable. nice one.

[@billboe9784]

Great video! Ive never seen a hardware calculator hack before.

[@RPBCACUEAIIBH]

If you press "+" then "1" instead of "1" then "+", then it starts from 0 not from 1 works the same way. You can also type in an initial number, from which to start counting, then "-" and "1" to count down, you can also use another numeric constant instead of "1" to count by that numeric constant.

[@ExStaticBass]

This is definitely something I wouldn't have considered doing before watching this video. They say the simplest ideas are the best and this one is brilliant. I think I would put the connector in farther so the pins wouldn't stick out the side but that's the only thing I'd change. I loved the Keysight O-scope hack too which I just finished watching before this one.

[@danielmoraes9637]

Great job!

[@abymohanan2043]

Thank you so much for this video 👍🏻👌🏻✌🏻

[@ravivashatkar5585]

I had the same idea Dave .... I never tried it .. thankyou for doing this 😊😊😊👍

[@tomwimmenhove4652]

I remember doing a project like this when I was around 6 or so. I connected one wire to our (aluminium) sink, and the other in a glass of water. By placing the glass below the tap and having it drip into the glass, the calculator would count the number of drops that have fallen. At the time I didn't appreciate the incredibly small change of current by the charge carried by a single drop. I'm still amazed that it worked at all :)

[@petermuller608]

Having a toy train: nerdy Using a calculator to manually count the laps: nerdy Hacking the calculator to count the laps of your toy train: king of the nerds xD

[@doggy_888]

WOW it's a really cool project!!!

[@faybercova]

what amazing video, congrats

[@krzysztofsoja5301]

Back in a days I used this method to make distance couter for my bike :)

[@genericgreensquid6669]

This was helpful!

[@Zadster]

Doesn't the calculator have an auto timeout? Unless you are watching it all the time, the little train will eventually stop, the key presses will cease and a few minutes later it will time out, losing the count number? The M+ button might have been a better option, as the contents will be retained.

[@EEVblog]

Good point. No issue for me as I'll be recording on video.

[@therealjammit]

I'm sure you could either buy enough cheap calculators until you find one that doesn't time out, or buy an old LED calculator on eBay. Pretty much any old LED calculator didn't have enough horsepower to do fancy things like power management. Might have to make an Ac adapter to replace the batteries.

[@akuunreach3260]

Nice Zadster, I was going to comment on the M+ being a better way as it keeps a perfect count vs the +1 Though Dave could just start with -1 so that the running total comes out correctly.

[@suplerb]

Zadster Whatt does M+ do?

[@akuunreach3260]

Mancobbler, it adds to what is stored in the memory. MS is memory store, M+ and M- add and subtract from the stored value, and MC clears the memory. So say you want to figure your pay but part of it is over time, so you take your hourly and multiply it by 40, and store it in memory. Then you would take your pay and multiply by 1.5 or w/e and then the hours of OT, and press M+ Now when you press MR (memory recall) it will show your pay for the week before taxes and withholdings. If you already knew some or most of this, I was simply trying to be thorough, plus others might read this post.

[@travis4798]

I use to mod electronics in the past. Best wire to use for pads is computer ribbon cable and if you go online to say Amazon they have ribbon cable by 20-50 foot rolls. Solder on with low heat, tack down in a few spots using hot glue, it will never come off.

[@magista247]

I did exactly the same 35 years ago with a Sharp calculator on my bicycle to measure the precise length to the basic school ;) So i was the first to have a 'bike computer'...

[@bornfe5127]

wow now ive got a counter for inductor and transformer projects thanks dave ("beauty')

[@MisterTalkingMachine]

We used to do calculator adding races in school this way.

[@welshgoldferret5107]

Awesome, I remember doing this when I was making Tesla coils on my homemade winding machine, worked well.

[@Zamsky39]

I really like videos like this one.

[@RinconingenierilEsp]

I love it, thumbs up

[@dheujsnrhfydhehehshshhdggsd]

really enjoyed a simple kid friendly project

[@mirkomueller3412]

Nice Idea - might come in handy someday.

[@horiamorariu]

Genious! Just remainds me that in a very old TEHNIUM (Electronics Magazine), back in 1980, in Romania, there is an article of WINDING MACHINE COUNTER - exactly the same, but based on Texas Instruments TI30. Nothing new under the sun. But maybe for some young hobbysts is new. Cheers Dave!

[@SlyPearTree]

I used that trick to make a cheap digital voltmeter in the 80's. If I remember it counted how many fractions of second acapacitor needed to charge from 0 to the same level as the voltage being measured (or discharge from measured voltage to 0). The fractions of second were probably relatively large since the calculator could not respond that fast, that was probably due to internal debouncing of the keyboard circuit. I think I took the idea in a magazine. The result was not really seriously usable but made a nice little experiment to learn a bit more about electronic.

[@shawn_2]

Super cool!

[@tonesoft1956]

New this when I had my first Casio calculator in the late 70s :D

[@aserta]

I used one of those electronic finger counters. Works perfectly well for those who don't want to do complex things.

[@mescalinum]

Very clever trick! Thank you. Would using an OTA (like the LM13700, which has an example for voltage-controlled resistor) do the job for triggering the "=" key with a digital input, or it is an overkill? Perhaps you could achieve the same with a MOS?

[@ryangriggs5767]

Very nifty idea! I wonder what the maximum input frequency is? (probably some multiple of the key matrix scan rate?)

[@fdjhrfgjry]

Hey Dave, another great feature of this ghetto-counter is that you can determine the +1 amount so flexible, eg. if used in composed counting formulas and tailor them (other than 1;) to match your purpose or eg. 6 decimal position or better precision. Almost literally a streetwise universal counter ;)

[@antonnym214]

Very nice! We can get these calculators at the Dollar Tree (everything's a dollar), so this is an awesome use for one.

[@waynerussell6401]

I had a client who wanted to detect how often a reference book was used. I embedded a watch module in the spine with reed switch and magnet and mode to set minutes. Only counted to 60 but that was adequate.

[@SimonE-fz5pc]

Funny found a box recently in the attic where my father did the same thing to count ants in a tube leading to food with a light switch for his Dr (PhD) thesis back in 1974! Sure it was an old "4 banger", as Dave says, but it still worked and high tech back in the days.

[@oogie-boogie]

just a question,,, i bought a hakko soldering station,, ,, but i need to know what size tips to get?,, what do you use size wise,, thanks im trying to learn to solder well,,,lol,,and not suck at it :)

[@Crazytesseract]

What's the difference in cost, if you use 4 bit 74XXX counter ICs in cascade, a bcd-to-7 segment convertor IC, and a few 7 segment displays, and wires, plus a bread board? And how do we latch the digits using multiplexing?

[@88njtrigg88]

Can be used also for a home made anemometer project, with the addition of a stop watch.

[@IGBeTix-Electronique]

Hi Dave, do you have the results for all these batteries ?

[@techalyzer]

I have done this on my bike ages ago, only instead of 1, I used to put in the tire's circumference to measure the distance.

[@UAUnstableMaker]

Oh, i did this thing as a child in early 90's, but it was used to work as an odometer for my bicycle. I just had to add a length of the wheel

[@karlramberg]

How fast switching speed will it keep track off ?

[@dismayer666]

genius in simplicity :)

[@BlankBrain]

03:29 should'a used your Crocodile Dundee knife!

[@tzisorey]

I had a calculator as a kid, that had a little thumb-trigger "Count" button - so you could take tally of things easilly. Had one of those old light displays on it too - doubt it was LED, but some sort of low-power red 7-segment things.

[@pivendren]

@EEVblog what was the reason for a different calculator at 2:15?

[@BeetleJuice1980]

what is the optimal "low" temp for these pads?

[@SkylerF]

I really need to drive multiple keys on a matrix-type input with digital logic. The problem with using a transistor is that it will only work with one key, because I can't use common ground. I know I can use optoisolaters, but is there any other way to electrically drive multiple keys with say several 5v logic lines, each for one key?

[@billl605]

Go green, power the loco with a solar cell, great video, and a thumbs up.

[@frogz]

heres a little hack for you, 301 green laser pointers(or any other cheap 18650 green laser pointer) aimed behind the board lets you see right through most circuit boards to see the traces

[@inderpartapsingh4445]

great sir

[@rockets4kids]

I recall an article on this from a magazine back in the 1980s. Does anyone happen to know the magazine/issue?

[@gorillaau]

Nice that the troll doll came along as a witness.

[@JONOVID]

IMO I would use hot glue to anchor wires in place. also I would use sockets as the wires end connectors so you can close the back up on the calculator and re-use for other counter type jobs in the lab.

[@tasteless_5915]

If you get a knife down the middle of the plastic heat rivets you can “drill” them out as it separates the outer ring from it and you can’t take the chip out.

[@jschroedl983]

OMG I loved those thomas the tank engine tracks

[@KevinOsborne1987]

Joe Schroedl AKA 'Brio'

[@thegreatdanet]

What's the deal with the copper pads for J1? Using a blob of solder as a jumper?

[@Luclips123]

Thanks

[@cody5495]

Question, if you were able to press the = button 1000times/seconds, could you overheat the calculator/max out the cpu? Do they have protections in place?..

[@LA6UOA]

Cool! Thanks, Dave! I really don't like tape. it falls off and in time its glue is a mess. Is there a reason why not use hot glue? and how fast is the calculator? Can it be used to count the rounds of say a propeller on a model aircraft? Love your channel!!

[@TheBendixSA]

Dave if you do some simple math and start the calc in constant mode with the right amount added, then that becomes a distance counter without ANY modifications. COME ON GIVE IT A BURL!!!

[@SpikesMavic]

Fantastic, just what I need, am wanting to count the amount of turns of wire for a transformer

[@Zauviir]

Is the batteriser fail train about to leave the station?

[@Jones12ax7]

as a kid in the 90s I used a crude switch on the front wheel of my bike and a hack like this. I type the wheel circunference, 2.1 at a time, and + so the I could measure the distance. I even placed a switch in a shoe to make a pedometer for a science fair of my schol. Good times before the microcontrolers invasion that we like so much today.

[@EgoShredder]

My uncle and I did something similar to make a digital speedometer for my bike around 1980 I think. We used little reed switches near the wheels to measure the speed etc. It worked perfectly and I was a proud kid, with lots of DIY gadgets! Good times :-)

[@nrdesign1991]

I made a bike pedometer that uses the AC voltage coming from the hub-mounted generator as a signal. It can't charge its battery through that yet though. I don't have any plans on working on it at the moment.

[@maicod]

as a kid I had a Fleischmann train and used 2 metal strips that when the train ran over it were pressed down and so the circuit closed and I let a railroad-switch flip over

[@tin2001]

I did the bike distance counter thing when I was a kid too. I wonder if I still have that calculator somewhere....

[@kaziq]

I once taped a switch (just two flat metal plates) to my heel, and wired it through the sleeve to an old bike counter stripped to my wrist. Then set an average step distance as the wheel circumference in the counter, and had a crude distance counter. And it was painful too after some time with the swith on my heel.

[@brainndamage]

I've used this method before for counting turns on a coil winding machine, the problem is that the calculator can only count so fast until it starts missing pulses. But for slow counts it is ideal.

[@o1napstar1]

I have a question: Why would you cover up the copper pads with carbon?

[@Zamsky39]

How fast can the signal be for the calculator to be able to still catch up?

[@moustafa19997]

nice idea

[@FennecTECH]

I would use lego and an solenoid to simply push the button each time lol

[@RyanUptonInnovator]

you forgot duct tape.

[@FennecTECH]

dont need duct tape when you use a lego flatboard as a base

[@RyanUptonInnovator]

I will attack your lego flatboard base with my duct tape x-wing fighters. Prepare your exhaust valve for my proton torpedos.

[@FennecTECH]

that sounds painful

[@RyanUptonInnovator]

At first it is like ow ow ow, but then it is oh oh oh. The worst bit is the child support.

[@user-vx8wr8wn5z]

Very good seeing in Brasil 😮

[@Andrew_Sparrow]

ive used the cheap dollar store step counters in a similar way, even easier to hack :)

[@blenderbuch]

In the time as the four banger got cheaper we used this to make km counters for our bikes, enter the circumfence of your tires key in + + + + + + Or was it M+? I cant try only UNP Calcs here now

[@MisterBadNews]

This is how we used cheap calculators back in '90 to count the number of coils on homemade coil winding machine. Using a calculator, a magnet and a reed switch attached to =.

[@graceful_songs]

it's the first time I knew that the holes in the pcb are test points .. I was wondering so much but couldn't know what to ask ... ahh thanks alot

[@Eicles]

Annoying that there always has to be some dislikes; this is bloody brilliant! I'll have to remember this one, might come in handy! :-)

[@vladomaimun]

Awesome video! Are you going to make more hacking vids?