Episode: 2514
Title: HPR2514: Electronics Calculator Kit
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr2514/hpr2514.mp3
Transcribed: 2025-10-19 04:30:25

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This in HPR episode 2,514 entitled Electronics Calculator Kit.
It is hosted by Enable and is about 33 minutes long and can remain an explicit flag.
The summary is Enable talks about building another 16 Electronics Calculator Kit.
This episode of HPR is brought to you by an honesthost.com.
Get 15% discount on all shared hosting with the offer code HPR15, that's HPR15.
Better web hosting that's honest and fair at an honesthost.com.
Hello, this is Enable and I'm back again with yet another Electronics kit.
It's got to be a series by now, right?
Once in a while I'm on some web page and this always becomes like an impulse by thing.
This one recently I was on Amazon like a few days back and I'm going to brush up on some
old electrical calculations just to refresh my memory like parallels and resistors
and parallel and series and amps and all that, just like a refresher.
And I started wondering, geez I wonder if they make a calculator where you can just press
a button and do ohms law real quick and stuff like that, so I looked on Amazon and yes
they do make calculators like this.
Electronics calculators and it turns out they make calculators for carpenters that figure
out whatever they got to do in the houses.
They make these specific calculators but they're $80 each and that's a little bit silly
and I'm sitting there with my phone in my pocket and I go, there's a calculator on my phone
and then I go, there must be a scientific calculator for my phone.
Do square root and stuff, quick app search and yep there it is but still it is nice
to have like a dedicated calculator and you know just have, it's easier to hit the buttons
than holding your phone and it gets a little fiddly that way.
Then I remembered my wife still had a calculator, Texas Instruments that does all the scientific
things so I just, I grabbed that and I figured out I'll use that a few days after that
I wondered if they had like a electronics like a workbook, just something that you know
it'll give you a problem per page and then you figure it out and then you know just,
so I go back on Amazon and I look and I did find one and I have that book now on the shelf
I can't, I'm not going to say what book it is or because I haven't even opened it up
I don't know if it's good or useful so but if it is, I mean that could be a follow up
HPR I have three books that I have one book, I've had for a while on electronics, the
art of electronics, I have another one that's pretty good, I'm looking at it now, hang
on, let me just grab, okay J.M. Hughes it's called Practical Electronics, that's good book
I recommend that one and then well I'll just mention what this book is but it's this
other book that I ordered recently, it's Mastering the Art of DC Circuit Theory by Paul
Rogoli but I can't say if that's this book or it's good or bad because I haven't even
opened the cover yet but there you go, anyways I forget how I found out about this book
it might have just been a search somewhere, I go on Amazon, I find the book, I click,
I add it to the basket, it's only like $16 and I figure oh let me just search around
maybe every once in a while I do this, let me just search around and see if there's
new electronics kits, something you know just for fun to build up and I think the algorithm
of Amazon, new I was looking at calculators and now I'm looking for an electronics kit
and weirdly enough an electronics calculator pops up a kit, so this is in front of me
right now, I haven't opened it, I'll tell you why I don't need it but I just thought it
was neat so maybe it'll be a fun little project, I can't imagine there's too much to assembling
this because there's not much in modern calculators these days, it's like one single chip
and then just buttons and a screen that's in a battery, sometimes not even a battery just
a solar pack but there is like a neat little feature to this one that it will be a neat
little calculator just to build up and leave here on the bench and but let's open it up
and I'll see you know how it look this is probably going to be like the build leaning towards
like a beginner's kit, so we'll see, let me see what's in here, oh actually it has a
lot more parts than I thought, you got to assemble all the buttons, keep digging in here,
it's like bags and bags, all right I've seen this type of construction before, it's all like a laser
cut on plexiglass and then you peel off like paper on either side of the plexiglass, I'm filing
all these bags right on the floor, that's how we do it here, here's the little screen, oh I've
seen this style screen before, I think I have some of these and it looks like it has the screen
drivers right on it, here's the chip, what is this chip, IAP, 1704HPBO55, I'm going to have to look
that up, then you get all the tactile buttons, button caps, the screws, here's the main PCB,
okay this doesn't look bad for soldering, and then okay a little coin cell for a battery,
a header, a few transistors, caps, and here is the neat little thing, these are,
where are they, instructions, and then this little thing that I thought was neat,
these are a little piece of paper, you're going to cut these, the numbers out, and the plus and
the minus and the square root and all that, and it goes underneath these clear caps and they go
over the tactile buttons, but on the numbers themselves are the resistor numbers, so one is brown,
two is red, three is orange, four is yellow, five green, on and on and on, so it would just be neat,
if you're wondering what a resistor is, just look over at these buttons and there's all your color
chart, I keep a color chart for resistors on a little cork board above the bench here, but I
printed it on a black and white laser printer, so I just have to like read the color and read the
number, this one's, it'll just be quicker or more, you know it's more fun, oh that's neat, they give
you a schematic too, you can see how it's built up, the pinouts of the chips, wonder if this is an
open source project, anyways, let me uh, I'll pause here, I'll just start building this up,
and I'll take a few pictures along the way and I'll talk about it after it's built,
alright, I'm just popping back in for a minute in the middle of this build, the instructions
are pretty scarce, sparse, and it doesn't say you get a pinheader female in male for the screen,
and it doesn't say whether to put the male in the board or the male in the screen or vice versa,
so I'm just going to take a guess and say the boards are going to get the female,
and if I get it wrong, I'll pull them all out and I'll tell you guys and save you the trouble,
but so far this is a, I'm gonna say that this is a good beginner's kit, you're not going to be
doing SMD stuff, you're not going to be doing a thousand components or, you know, exaggerating with
a house and there's no, I don't think there's any kits with a thousand pieces, uh, but you're not
going to have like, you know, 40 different types of resistors and you can confuse things and it
takes you forever to sort it out, so far it's, so far it's been an easy build and, uh, it's going
to be a while soldering up all these buttons, but I'll see how it goes, alright, back to the soldering
pen, okay, these buttons are a bit of a trick, I usually use that soldering cradle, I have mentioned
it before, it's like a blue little stand that you can put the board in and spin it around,
load the components, spin it and solder them up, but these, I tried putting the tactile buttons in
and holding with my finger, but what I found is I just, the easiest thing I found is I just loaded
all the buttons, carefully flipped it onto the table, then you can push down on the whole board
with your finger, you could probably hear all the buttons clicking right now, just to make sure
that they're seated and then put the soldering pen and you can use the pen to hold down
as well and then use your other hand to put the solder on and then just keep going like that,
otherwise you're going to end up having to either hold all these with your finger or put tape
over them, which sometimes works for one component, but if you have a whole row, like these are
foreign or row, sometimes that, you know, the two ends will be held by the tape, but the middle ones
will bulge out, so I'm finding this easiest, load all the buttons, flip it over, put it on the table,
and you can just push the whole entire thing down with either your finger or the soldering tip,
and I'm about a third way through these, so let me keep going.
All right, I'm back. That was actually a two-day gap there. This usually happens in the HBR
as I record. I got to the point in the build where it needs batteries and I didn't have any
of the battery. It says in the instruction here, power supply is two CR 1220 batteries.
So I went back to Amazon and I ordered CR 1220s and I have them here now, but they look like
they're not going to fit. They look too small. I also have CR 2032s, which is the ones used for
motherboard bios, and I have some A76 or LR44s, but those I use in my digital micrometer.
So let me see if these, it says in the instructions that you use these 1220s, so let's pop one open.
I'll take a picture and if you look at this picture, you'll be skeptical just like I'd
am because it looks like these want CR 2032s, which is that one we're all familiar with,
but the size of an American nickel and they're used on motherboards. I don't know where I put the
camera now. So on the right there are the CR 1220s that it's calling for. They are
really tiny and they're really thin. You can see on the board,
not maybe they'll fit, but this is kind of ridiculous. Let me just try. Well, they do fit, but
you like lose them inside the socket. They go that far in. I wonder if a, let me just try one of
these bigger ones. These are about three bolts, right? Yes, I'm talking to myself because you're
not going to answer me. Yeah, they're all three bolts. So let me see if a,
yeah, these sockets are for CR 2032s. I don't know why the instructions told me
to get these really tiny ones. They do fit, but they just, you lose them in there, they get buried.
All right, let's see if it powers on. So that's on or, oh, I got to put the screen in and I got
to put the chip in. It's been a couple days, like I said, so I forgot exactly where I was. Where's
the chip? I think we should strike a deal. Every time I do an HPR, one of you should come over here
and clean this desk. It's a mess. Where is the, I have no idea where the chip is. Can't go
further without the chip. It's kind of a needed part. Let's go over here. Oh, it got stuck
to a plastic bag with electric tape and it was on the floor. Good thing I didn't step on that.
All right, let me pop this in. We just got to squeeze the legs a bit to get into the sockets.
I don't know how the pick and place does it. It must squeeze them as well, I'm sure. Oh, I remember
reading one of the, I'm sorry, I'm doing two things at once. One of the Amazon reviewers saying
I didn't like that you had to bend the pins. I didn't know what they were talking about. I'm doing
it right now. I have to bend these pins. It's like the pitch. The socket is not the exact socket
you need, but I thought that all this is pretty standard. Wow, one of the pins just bent,
tried to go into the wrong hole and socket. Yeah, this is what that reviewer was
complaining about or am I need to know. Wow, that could stop the project right there at that pin
broke. It's just almost sore. It bent again. There's this a different one.
Okay, there's the top side. Wow, that was pain in the butt. Okay, you guys are worn too,
so it would probably have been better if I got some needle nose and pre-formed them, but I was
just trying to use my fingers. As soon as I put the LCD screen in, the LCD screen lit up,
and I got nothing. All right, so I'll have to do some troubleshooting, which I enjoy because
oh, now I see possibly, maybe not. No, I think these want the bigger batteries to CR2032s. Okay,
I'll press pause again and check around and see why this is. Oh, it just went off. Oh, it's on.
And I have two zeros. And I'm able to input numbers. Oh, there's two, five, three, plus
I'm just pressing buttons because I don't have any numbers on them yet, so I'm just pressing
random buttons. Two, five, six, plus four, four, which one will be the equals sign. This one
is 300. Okay, I think this is working. I think I can put it in the case now.
I like that the screen lights up. It's backlit. I've been using the, just take another picture there.
I've been using the, my wife's camera, like the scientific, or not camera calculator,
that scientific one. I've been using that. I started getting into that book that I told you about
the mastering DC or whatever it was called. So, but that screen doesn't light up at all. So I'm
constantly like, you know, picking it up or turning it to a different angle. I wish that one
had a backlit to it, but this one does have a backlit. I've seen this screen before and it dawned on
me yesterday that this is the same screen that's in a function generator kit that I built,
which I don't think I ever talked about. That could be another HPR. I'm,
there, I'm locking myself into some more. And they're okay, it just did the auto timeout. So if I
hit this again, okay, I think this is working. And I think it wants the bigger batteries. However,
I got one big battery on one side and one small battery on the other side. So I suppose it can take
either, but you're going to have to get, when you want to pull that little battery out of there,
you're going to have to get some piece of like metal or something, grab it, hook it and pull it out.
So all right, I'll now, I guess I got to look into how to build this plexiglass case. There's
like standoffs and stuff, but there is no instructions on how to build the case. So and then
the other thing that you do is you have to cut out like the one two three four five plus minus
divide the square root, all that. You have to cut out little pieces of paper and those go into
clear buttons, those go into blue buttons, those blue buttons snap onto the tactile buttons.
And then hopefully this all fits in the case and I can come back and let you guys know how it works
and try and I'll go through some functions trying to square root and or screw as a hero who says
somebody on, he's a fun guy to watch. He's on YouTube.
Doc Schuster, I think he is a teacher's physics, but then after his classes he does
like a five or a ten minute video about what that class was, probably just to help the kids if
they want to go home and you know review the lesson again. This is neither here nor there, but if
if you're interested in like science and all this kind of stuff, check him out because he's
entertaining. He does do a small series on electronics like resistors and parallel,
resistors and series and stuff like that, so just when I said square root and I thought
screw, that's how he says it jokingly, it just reminded me of him, so I just thought I'd mention it.
All right, I'll be back after I figure out this Plexiglass case. I've just started
playing with the Plexiglass case and I glanced over at the instructions and there's a QR code
and I wondered what that was and right above that is a URL and it is detailed diagram instruction.
So I've been trying to go off this Spartan instruction sheet here which I'll go to the whatever
this URL is and once again I'm doing two different things with peeling the stuff off the Plexiglass.
I'm going to check out this URL and see how detailed it is and maybe it'll just I've gotten
the build together just intuitively so far, but this case has a lot of parts and I'm not sure which
screw there's two packs of screws, black ones and silver ones. So I typed in that URL and I get a warning
what was it worded say back go back. That this is a risky site and it has bad software on it and I
ignore the risk and I get a 4.00 and it's in Chinese and this is a reported attack site.
So get me out of here if this is an attack site. I wouldn't do what I'm doing while I don't use
windows but I feel a bit safer with Linux. So I clicked forward. Wait, please don't visit this site
now Google detected heart but all right it's like warning after warning don't go to this site.
I'll just I'll just back out. I'm sure I can figure this out on my own and if I run into
anything that's not intuitive or you know it gives me more trouble than it should. I'll mention
it here in the podcast so you don't have to struggle through it but I'm still this is taking
longer than the build actually. I'm peeling all this cardboard backing off of this Plexiglass.
I'll be back when the thing is built. So I'm back again as usually happens with when I try and do
a podcast there ends up being pauses in it of days or weeks. This one was two weeks so it's been
up it's been a while but I came back to the project. My wife has signed up to take a jewelry class
at a local like art center and she goes every Saturday so I thought while she's away it would
be fun to like try and do a HPR while she's at the while she's at the class and I just have
idle time. So that's what happened with this kit and that was what I don't know three weeks ago
but then last weekend she had some type of flu thing so she didn't go to the class anyways she
just left. I'm recording again I have the calculator I've finished it in the meantime and I can just
talk a bit about the build and some other things I found along the way. I'm still going to call
this a beginner's kit for the the soldering if you're going to if you want a kit to solder up
you're not going to get it you're not going to have any little tiny SMD parts on this you're not
going to get into fiddly you know soldering up ICs you can do it with just a regular tip that's
going to come in almost any soldering pen the case build however is very fiddly it's a bunch of
little tiny screws and a bunch of little tiny nuts and I mean it's nice the way it all fits together
but screwing it all together gets it was a pain in the butt and I had to do it like two or three times
because there are standoffs that's the first thing I made a little list because I knew I wouldn't
I wasn't going to be recording for a few days so here's the four things on my list there are
standoffs there's tall ones and short ones the first time I built this up I put the tall ones on
the board with the buttons and I put the short ones on the LCD board and I had that backwards so I
had to tear it all apart again and put it so I got a picture of that in the show notes just show
you the different standoffs put the put the how would you say that the shorter yeah they're
standoffs put the shorter standoffs on the board that goes on the base of the whole calculator kit
and then put the taller standoffs it's for the LCD screen they are the depth basically of the LCD
screen let's the LCD LCD screens fit flat on the front face instead of us sunken in or pushing out
the second thing okay I built it all up I got the standoffs right I start to go populating the
buttons here's the second thing on my note just I know I well I think I did I'm pretty sure I
mentioned I don't even know what I recorded weeks ago that I put all the buttons on the board
and I used electric tape to hold them and I flipped it over and I soldered them up quick don't do
that it bit me right here I put the whole thing back together I start populating the buttons on
the calculator and button eight and nine button five and six and button two and three which are all
grouped in the center we're all leaning a skew because the tape was not supporting them over there
it's probably best to solder these one at a time and make sure you got that button pushed
down into the board solder it up because if you have it crooked at all you can't get the buttons in
if there's a pretty tight tolerance between the the face where the buttons go in and the buttons
themselves so that's tip number two tip number three I put it all back together I got the buttons
going the thing only lasted like four minutes and then the battery was dead I took it apart again
I put the other batteries in again four minutes I think these instructions that came with this kit
are an old set because like I notice the square root button is different in the instructions and
it is on the calculator I bet whoever built this
specked out these what was those little those little batteries you'll probably remember quicker
than I did because you just heard it about 10 minutes ago oh it says it on the sheet
CR122 CR122 zero batteries they're pretty tiny I bet you well they would probably fit in a watch
like a wristwatch and then I remember speculating that they originally spec these out for the CR
2032s which you'd see on motherboards and anyways I put the whole thing together with what the
instruction said and it only lasts four minutes those little tiny like watch batteries I don't think
they can power that light on the LCD for too long so I tore it all back apart I went and got the
coin cells the CR 2032s and they do fit you push them all the way in and I'm looking now yeah
they fit fine I think there was probably like a design change because the other batteries weren't
lasting and they just didn't update these instructions I bet if I could get to that the web page
where the online instructions are they probably clear all this up but I kept getting that attack page
thing attack page so I just braved it alone so if you can't get to the new instructions and you
don't want to brave that attack page I'm trying to help you out here if you buy this kit and
okay that's it for my notes except for one thing at the very end so usage
well you press on of course I have it here next to my I have a Texas Instruments TI 36X
this is the one I use when I'm doing calculations I don't really need all the power of this
like I never do some of this stuff that you might do and what I'm saying is there's buttons here
that I never touched but this calculator was only at 25 dollars I use square root a lot I use
parentheses I like to try and do my calculations as like a one-liner on the computer the calculator
and anyways after building up this kit I like it it's fun it's a neat kit it's going to be cool
to leave on the table but when I'm doing calculations I'm still going to be grabbing this Texas Instruments
I'll tell you why so let's just go through the functions of this thing here you press on you can
just do you know any 25 times three you get your result you press on it clears it again there's
back space if you if you put a wrong number and you can hit back that candy the thing that I thought
was neat when I saw this kit is each of the numbers if you look at a picture there each of the numbers
has a color band on it and those are the color bands of resistors so one brown two red three
orange on and on it would it's just neat if if this is on the desk somewhere and I'm I do have
the resistor chart you think I'd have it memorized by now but I have the resistor chart up on
a cork board but it's printed in black and white it'll be neat just to look over and what was green
again five you know just look over at this calculator the other thing you can do is you press on
you press the mode button and then you can enter a resistor's value that you have in your hand so
let's say yellow well this is the one in the instructions yellow violet black and brown and then
you press one of the other buttons which is the multiplication the division those will give
tolerances so in this case they're saying put in brown for so there it tells you what the
resistor is 4700 at 5% you can I just turned it off press mode then you can do that was a five
band resistor if you want to do a four band resistor you press the square root symbol but it's also
a selection button so you press that and you see the color band ring changes to four and then
you can put in green red yellow again this is the one in the book here and then you choose your
tolerance so 5% so I got a 420k resistor at 5% just another neat little function of this another
thing you can do is calculate the working voltage of LEDs and you can also convert from a decimal
to hexadecimal with this it does have in regular mode it does have square roots a square root of
100 is going to be 10 so there that works the thing that's missing on this that I use all the time
is parentheses brackets so until you want to calculate some resistors in parallel
let's say you got a I'm just going to pick these numbers for ease of use of four ohm and a five ohm
so you'd go one over four equals so then you got to write that down 0.25 and then you got to do
your one over five then you got you got to write that down again 0.2 and then you got to add them
together so 0.2 you can do this in your head but I'm just doing it on the calculator plus 0.25 equals
0.45 then you have to do the one over that again so one over four five equals
0.022 and then they put a plus because they mean the pluses are going to go on but on the Texas
instruments how I would do that is one over open bracket one over four plus one over five close
bracket enter you can see how much quicker that was I got I got the answer hang on these answers
are different ah okay the answers are the same I'm using my Texas instruments in degrees and when
I put it into engineering I get the same when I put it into engineering mode I get the same result
as this calculator so they might be given your engineering results which would make sense but
I tend to use degrees anyways I will miss the brackets on this thing the parentheses so there you
have it it's a neat kit it's a it's neat that you can look through the plexi glass and see all the
insides and it's it'll be a neat like conversation piece I will use it you know if if my text
instruments is in another room I'm sitting here on the bench I will use this the case is fiddly
like I mentioned every time you want to change the batteries you're going to have to take it apart
and put it back together I've considered making little slots inside the
oh yeah here's here's one fiddly bit when you put the LCD screen on you put a screw through
with all the to the plexi glass through the black front into the clear plexi glass then you have
to take this little tiny nut and stick it in a slot and then get the screw to go in there and
all the time I would drop that little nut inside the case it would rattle around I have to pull it out
I ended up taking some electric tape and wrapping around my finger sticky side out and then putting
the nut on the tape and then sticking that in the slot and using a screwdriver that worked out
better but just be warned every time you go to change the batteries you got to take this thing back
apart but for a $16 kit it's fun go go buy one the last thing on my notes was I know I mentioned
books at the beginning when I recorded weeks back and one of the books that I mentioned was
mastering the art of DC theory and I said I couldn't say anything about it because I hadn't even
cracked open the book that is not the beginner's book this one does not hold your hands it assumes
prior knowledge so just before warned if if you're gonna investigate any of the books I mentioned
in the beginning this will give you a problem on one page and go through the solution and then
you flip the page over and you get the same problem with different values you have to solve that one
on your own then look in the back of the book and see if you got the answer right I'm enjoying it
I'm up I'm looking at I'm up on page like 76 now it's good fun if you got some prior knowledge and
you just want to brush up on some circuit theory and calculations and stuff like that this isn't a
review of the book I just thought I follow up because I know I mentioned it I suppose I can review
some of these books maybe when I'm done with this one or a little farther in but anyways this isn't
a podcast about the books it's about this calculator I'll put some pictures in the show notes
if you guys want to contact me I've mentioned my email so many times you can find it but
really I enjoy the the HBR comments section more so I've been using that
because we just keep the conversation going there okay until next time this is NY Bill signing off
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