Hi, let's say you've got a little La Toya train set up like this and you want to actually count the number of laps that go around like this now. I've actually stuck a little magnet on the side of there and I've got one of these magnetic wreath switches here that you can that you use for your home, burgle, alarms, or whatever any type of magnetic reed switch. So when it goes past it, closes the contacts in their shorts, it out is just a switch and you need to count how many laps. How do you do it? Well, can do it the complex way which are shown in my previous video using a universal counter and all that sort of jazz to do that.

But I thought it'd be much more interesting to hack a calculator to do it. Now let's take a look at this casio. SL 300 N Cbins should work with any calculator if you just go one plus like this and then press plus again, it will be in the constant mode and then you just press equals like that every time. and Bingo! you've got yourself a counter.

So all we've got to do in theory is hook the output of our switch here across the equals key inside here and Bingo! We should have ourselves a nice little train lap counter. Let's give it a go. Quick tear down inside this this is a Joule our solar and battery powered system. hence a little low diodes in here isn't They didn't bother with our surface mount, they just use it through hole and solder them directly onto the board.

That's really interesting. Ah, another interesting thing to note in here is this Led here. they've got why they've got a lead in there. I Think what they're doing there is actually clamping the output, using it as a like a 1.8 volt or whatever.

our diode clamp to clamp the output voltage from the solar cell here, so that's interesting, but there's nothing else in here. We've just got the main IC chip on board. it's just been blogged and somewhat annoyingly and not really ideal for the purpose. This model has the carbon covered copper pads here, so these are vias here and individual little test points there.

Very nice all the way around there, but yet they're covered in carbon so you have to scrape those off to be able to sort to these pads. He is and this one's a little bit annoying. Doesn't have screws holding it down. It's got these PCB are heat steaks here, but you can actually just get a knife in there and shir OHS off.

But yeah, this is not the best calculator for this job. Hmm, now with this what you're better off doing. instead of like removing the key like that, you're better off just find in which tracks actually connect under there because these are carbon so you know to try and salt are under those. That's the equals key there.

try and solder on to that, have the wires coming out front. Not the best option. probably better to end. Of course you can still keep the equals R key intact if you can find the two appropriate matrix R traces that come out and access them on the bottom side and then scrape off some of the carbon on there and then solder wires directly onto the pads if you can.

So in this particular case, that's our equals key. There we go that goes down or Via down there and that one goes down to V R So those two videos, we can access those on the other side. Thank you very much. Now fortunately, we've got two pads here connected to the two vias that we want.

Isn't that convenient? These are all our test pads so that they can test this with a bed of nails tester so we can just scrape the carbon off those pads. Just get in there with a knife, be very careful and you can expose. Check it out. You can expose the copper under there and we should be able to solder to that pad very nicely.

But the problem is solder in two pads instead of putting wires down vias is that it's not very robust. so you definitely want to use low mass wires soldered on to those, so then when they flap around in the breeze, the weight doesn't peel off the pad. You want to use a very low temperature on your iron as lower temperatures you can get away with so you don't lift the pads and also you want to anchor down the wires later. So I'll just do that, scrape them off and solder it on.

Bob's your uncle so there we go. I've modified that, just tacked on a couple of mod wires here. I've got it going off to a connector here because as I said, if you've got a lot of strain on these wires, I mean you can't just take them directly off to whatever a switch you've actually got, but that don't get to tape him down. Otherwise, there'll be stress on their shoulder joints and they will just fall off the first time that you handle.

Just peel the trace off and the pad off the fiberglass and yeah, and really ruin your day. So better to have some sort of connector interface. I've just got a point. One inch our header here.

You could use like a screw terminal or something like that. You could do a bit bit nicer than that if you want, but anyway, that'll be able allow us to reuse this as a sort of like a universal counter. I Mean we could even sort of hack out the case and put the case back on and stuff like that and we can just insert a switch on the side. Beauty.

and by the way, in this case with the carbon covering the Vias, that's going to be down the Vo holes as well so I wouldn't go sticking your wires down there and soul during them into the Vias. I would have scraped off if we didn't have those pads out. We'll just just gently scraped off the top of the Vias being careful not to Nick the wire in there and just lay the wire our flat on top. All right, let's give this a bow.

We've got it hooked up without a connector on the side. Very nice look at that so we'll just go one plus plus and of course you might have to subtract one from the final result. but hey, no big deal. Ah, that's a real Bobby Dazzler Fantastic! So I hope you'll like that How to hack a calculator into a simple counter.

And yes, it is just a switch input to this thing so you can't use like a digital input or anything like that. It has to be just an open contact switch and if you had some er sort of other input that you wanted to drive a noisy input you might want to clean up first. then you can just do the output using. You can short it out using a transistor or a relay or summer any sort of other system that gives you sort of like more or less a contact art type output because remember, this is a matrix keypad.

It's not like just a individual keys with pull-up resistors or anything like that. They're not digital inputs. So there you go. I Hope you enjoyed that.

If you did, please give it a big thumbs up because that really helps a lot these days. Catch you next time you.