hpr_transcripts/hpr1858.txt

Episode: 1858
Title: HPR1858: Multimeter Mod's Part 2
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr1858/hpr1858.mp3
Transcribed: 2025-10-18 10:17:06

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This is HPR Episode 1858 entitled Multimeter Mods Part 2.
It is hosted by AniBill and is about 23 minutes long.
The summary is AniBill finishes modification due to his multimeter.
This episode of HPR is brought to you by AnanasThost.com.
Get 15% discount on all shared hosting with the offer code HPR15.
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Hello, this is AniBill and I thought I'd do the follow-up to an earlier episode I did
about Multimeter Mods Part 1.
I didn't expect that to be a two-part show, but if you listen to it, I ran into a few issues
at the end and it was long enough already, so I had to order some parts and wait for those
to come in and then order some more parts and wait for those to come in, but I'll get
to that in a minute.
So the parts I was looking for were an on, on, momentary switch, because what I wanted
to do this meter, in case you haven't heard the last episode, was install a backlight,
which I did in the last episode and install a MOSFET that would allow...
This meter does not have an auto off.
If you leave the dial in a function, it'll just run until the battery dies and I kept
doing that because I'm used to my fluke meter that I use at work and that auto times
off, I'm just used to throwing it back in the bag when I'm done with it and the battery
lasts forever.
It turns off after three minutes, I guess, five minutes.
So this Unity UT-61E does not have a timeout feature.
I wanted to add one using a MOSFET and having a momentary switch when I pull it in, it
charges up a capacitor, the capacitor drains through a resistor, and the voltage, as the
capacitor is draining, is going to be in the threshold of the MOSFET that's going to
pull in the MOSFET and act like a switch.
So the first thing I had to do was find...
Well, what I originally wanted was an on, off, momentary switch, and I couldn't find
one of those anywhere.
When you go to my episode Gathering Parts, I talked about Digi-Key and Mouser, I used
them a lot.
There are some other ones I just don't tend to use them.
There's Element 14 and there's some other big components distributors out there that...
What's that other one?
Starts with an M. I'm not going to remember it now.
When you go to the M and you look up, I wanted to go to Switches, so I go to the Switch
section and then there's like 100,000 switches.
So you start using the filters to narrow things down.
So I went to...
I'm trying to...
This was almost a month ago now.
I'm trying to remember how I did it.
Oh, I selected what I wanted.
I wanted an on, off, momentary, and when I went to that filter, there was none.
But what I did see in that filter was on, on, momentary.
So I talked about in the last episode how that will effectively work as an off.
I just didn't use the center terminals.
They're not doing anything.
When the switch is in the middle position, there's no power going anywhere, so that's off.
So I've clicked on that filter and usually what I'm used to is you're looking for a part
and there's 70,000 results and you start filtering and you go down to 30,000 results
and then 20,000 and you narrow it down till you get to a point where you know, you're
maybe at 100 different devices to choose from.
Then you can just start looking through price and you know, you can find your part that
way.
When I clicked on this on, on, off, on, on, momentary switch option in the filters, I went
down to four devices.
So that was not helpful.
I really had trouble finding this switch.
Of that four, one of them looked, it didn't look exactly like the type of switch I wanted,
but it's just a little black switch you're probably all used to on cheap devices that
you've been seeing since you were kids.
I mean, that's what I recall.
So I looked at the picture, it's on, on, momentary, it's just that basic black switch.
I thought it was going to look a little bit ugly, but there's room in the case for it.
So okay, I just, I ordered it.
So I waited for that to come in and it came in, it's twice as large as I thought it would
be.
So this is one of those cases where you should check the data sheets.
Actually, this happened to me a couple times on this modification.
Check the data sheets and go down into the actual physical size of the device you're
buying.
You know, when doing projects in the past or, you know, ordering parts, I look at the
part and I go, oh yeah, I've seen that part before, that'll work and I order it.
And if it's a little bit too big or a little bit too small, you just adjust the size of your
project or you get a little bit bigger project box or you, I can deal with it in some different
ways.
When this switch came in, I'll have a picture of these switches in the show notes.
It was much bigger than I thought it would be and I started running into space issues
inside the meter.
So on previous projects, when you can just modify your project a little bit and change
the size of your project box, you can't do that in this.
This is a built meter and I only had so much space in there.
But I opened the meter up and I take some measurements like with my, my crometer can
take like inside measurements.
So, and I did look like I was able to fit this switch in there.
So, not having many choices for switches anyways, I was just going to go with it.
So I opened the meter up and here's where I got in trouble the first time.
I turned the meter over, it's lying on its face.
I pull out the screws and then I open it up like a book.
So I opened the back up to the left and I'm looking in there, I took all my measurements.
It looks like the switch is going to fit.
I carefully, you know, draw where I want to make this opening in the meter.
I take the back, I go down into the basement.
I'm using exactonize and a dremel and some files.
And I make the nice hole and I come back upstairs and put it on top of the clothes, like put
it back the way it was laying on the table and then close it up.
And because I had the meter open in a bookmark fashion, when I closed it up the right side
where there was a lot of room in the back of the meter now becomes the left side and
the switch would run right into the speaker, you know, the beeping continuity speaker of the
meter and like my head went down and like, you know, what am I going to do?
So lesson learned there, paid attention to which side you're flipping things.
So now I was going to have this big ugly hole on the side of my meter.
Then I remembered my buddy Acefear from our lug recently got a 3D printer kit.
So I fire him off an email and I said, look, look at this bone head move I made.
You think it would be possible that we can make a little switch plug to go in here.
And he said, oh yeah, definitely that would be a perfect project for the 3D printer and
he just got it.
So he's new to it too.
So, you know, it was fun to have a project to do.
So the next step was he was on, he was away at work.
So he wasn't going to be back for like two weeks or something.
And then I start thinking, well, I don't want to say, hey, can we make this plug to go into
this meter with your 3D printer and oh, by the way, you design it.
So I figured I didn't want to just drop the whole thing in his lap.
So I had a good week long and weekend like cram session trying to learn about 3D printers
and trying to learn about the software you use for 3D printers.
So that was a little nice side diversion from the mistake bone head mistake I made opening
up the hole on the wrong side of this meter.
So I did all my reading up door in the week and I looked at a whole bunch of CAD programs
and some of them I was just completely lost.
My buddy Ace Fear uses, I think it was called S-CAD and when I loaded that up, I asked him
what he used.
He told me what he used.
I loaded it up and it was just like a two-pain blank GUI.
And then he tells me after I was just completely lost and I said, well, that was not the one
for me.
Some graphic design from college and I'm always gimping something or I'm in inkscape.
I wanted something more leaning towards that and he tells me that this program that he
uses, you just programmably programmatically type in what you want, like square this size
by this height in this location, rounded corners, somehow you like, he's into programming
so he felt more comfortable there, like programming the 3D shape.
I was thinking more like modeling or woodworking and I wanted something to, you know, put up a
shape and change it in different ways and have all the options that I would in the gimp
or inkscape.
And what I settled on was Blender and oh my goodness, Blender is there's options for
options for the options, there is so much stuff in there it's daunting.
So that was like three or four days just watching like tutorials on YouTube and just reading
up on how to even get around the GUI of it.
Just tools can slide in and slide out, it's like the gimp on steroids.
So anyway, I learned enough to do what I wanted to do, I learned how to, you know, put
blocks down, how to like put another block inside the block and extrude it to leave a
hole there.
I have a picture in the show notes of the switch plug I made and also the following week
after that, I started thinking, well why don't I make the switch plug for the right side
which is the wrong side and then on the other side going back to either DigiKey or Mouser
whichever one I was on, of those four switches I was able to select from, two were the large
size and two looked smaller.
So I said, well why don't I get the smaller one and I'll see if I can put that in the
left hand but it was so small it didn't have like a tip on it.
So then I'm thinking, okay maybe I can 3D design a little holder that's going to hold this
switch and then 3D design a little nub that's going to go on to this switch and then put
that all together and then put that in the side of the meter.
I'll have, oh there's a picture because I was like kind of shocked, I'll put it in
the show notes again.
The new switches get here and they are so tiny, I just went to extremes from a huge honken
switch to this little switch that like one time I dropped it and it took me, I had a
flashlight out to try and find it on the floor.
So I went from a large physical switch to something that would more likely be surface
mounted like inside a phone or an audio player and do exactly what I was thinking have a separate
piece of nub that sticks out through the case.
It's hard to explain but if you look at the picture you'll see it's just super tiny.
So that was more 3D modeling, I 3D modeled the switch plug to go in the right side which
was the wrong side and then I 3D modeled the switch plug again but then modified that
to accept the small switch and then a little nub that would actuate the actual lever inside
the switch.
And I sent that all off to Asphere and he said when he got back to the work, he said
anybody, when he got back to the factory he called it, I had a laugh at that.
When he got back to his house he would 3D print these designs I made.
So I had to wait for the lug, he printed them up, he did take pictures and he took a video
if those are still online I'll link to those, if anybody wants to see the 3D models being
printed up.
So Asphere printed me those parts, he brought them to me at the lug and we fiddled around
the plug fit in the meter perfectly and then the switch holder, that was going to need
just a little bit of modification but it did hold the switch but the button wasn't the
button that I made to go and the end of it wasn't rocking properly.
So I figured I'll redesign this a little bit and he said he print me off another of
the redesign but I won't get that for another two weeks I guess.
So however, when I was putting these pieces into the meter, the switch blank and the other
piece that I made for the smaller switch, that was also based off the switch blanks or
the same size hole.
I had to get rid of some plastic inside the meter, I just had to nip a few pieces out
with my wire cutters and then I found out that once I did that with this large plastic
part for the switch housing, that old switch that was too big did fit into the meter.
I just had to clip off a row, it was a double throw switch so there was four terminals
on one side, four terminals on the other side, they were independent of each other and
they both had the same function.
Top two terminals on the left would be maintained closed when you push it up.
The middle would be maintained closed when you're in the middle and down the two bottom
lugs would be momentary and it would snap back to the center position and the other set
of terminals on the left, what did I just say, left or the right, but you know the other
side did the same thing, they were redundant so you can use those in other, if you had
an application where you needed that, I guess.
I didn't and I was able to just clip off the, let me see which side it was, trying to
think I'm going to hit.
I clipped off the left side looking from the back, clipped off those four terminals and
it stopped hitting the components, it was hitting when I would close the case.
So while I was waiting for Asphere to print up the modified tiny switch holder, I figured
why don't I just carry on and I'll use this large switch for now because now it's fitting
in the left hand side of the case and I can continue with the project and once that little
switch modified switch holder gets in, I can open the thing back up and play around a
little more.
The other problem I mentioned at the very end of the last episode, part one of this,
was that the MOSFET was working fine on the breadboard.
You pull in the momentary switch, the capacitor charges up, it pulls in the MOSFET, power
runs through the MOSFET and was lighting up an LED just fine.
I was able to tweak my timing, use changing different resistors and I got something around
10 minutes which since that time I figured was too long, I'm now down to the five minute
mark but that's neither here nor there.
So everything was working fine with that circuit, that could have gone right on a breadboard
and I was going to have it run the meter.
But I thought at the end I better get rid of this LED out of the breadboard and run some
alligator clips actually up to the meter to make sure that that MOSFET could handle the
current drain that this meter is going to try and draw when it turns on and it didn't.
It took the voltage from 9 volts and immediately like socked it down to 6 volts and then tick,
tick, tick, tick, tick, the voltage just kept going down from there and the meter just
didn't even power on.
So I looked into what this MOSFET was, I got a written down somewhere, okay here it is,
the MOSFET that I had at first that was having trouble providing enough power was a 2N7000G
and it says it's a 1GHz end channel, 1090 seconds switching MOSFET.
Just looking around at this, I figured this is probably a MOSFET that's supposed to
be used in like high speed low voltage applications which this is not.
This is just slow, I need, basically I need a little tiny relay but I don't want a mechanical
relay so I'm using a transistor.
So I looked around some more and started going through all the transistors I had, it wrote
on the numbers and then I was looking at them individually online and one that looked
like it would be more suitable for this purpose was a 2N3904 and then I also saw the online
that says there's a modern equivalent to that that does better at switching but that's
a 2N, oh my handwriting is so sloppy I can't even read that no, 2N2222 but I don't have
one of those here, however I pulled out the MOSFET and I stuck the 2N3904 which is switching
transistors which is specifically designed to switch things, not at high speed or anything
I think it's like I just said I wanted a minute ago, it's a relay that's not mechanical.
I stuck that right in place of the MOSFET, turned everything on and it worked fine, put
my allocator clips back up to the meter and bang, it worked fine.
So I found all my components for my circuit and the next step was going to be pull these
parts out of the, oh this is where I did some further timing too by changing the resistors
I had to actually put a few, I'll have to look into what sizes those were, maybe I'll
write those up in the show notes, the components I used but I had to put a few resistors in
series to get enough resistance to, because the capacitor was draining too quickly.
It wasn't draining too quickly with the LED just sitting there but when I put a load
on it it starts to pull, everything starts to pull down, however this new transistor
is going to work.
So the next step was I got a piece of Perfboard and I pulled my parts out of the breadboard
and got them all in there and soldered up, you can see pictures of that, I took pictures
like every step along the way, plus it helps remind me when I see them, what I want to
blab about here.
So that part soldered up and then I took it into the basement, actually Perfboard is good,
you take your wire snipers and if you have a line of Perfboard has all the holes in it,
actually that might be the wrong term for it.
Perfboard might be all the holes with no copper, but I used the one with all the holes and
then each little hole has its own little copper pad already on there.
That might have a different term than I'm not thinking of but I think you know what I'm
talking about.
But if you have the Perfboard I used was like two inches by three inches and all I need
was like an inch by a half inch.
So I built up all the components up on one corner of the board and if you take a line
of those holes and just take your wire cutters and just start cutting in, it'll just kind
of crack right up through the board and you can split it off that way.
So I cracked my parts with the components off the board, I took it in the basement and
just on the belt sander I was just cleaning up all those holes, leave little jagged edges
plus I needed to make a little notch in the top of the board that's going to fit into
a piece of plastic that's sticking out inside the meter and then I found that if I just
rounded off one of the bottom corners, this board would sit right back down into the
back of the meter and be plenty of room for everything to close up.
My next step was to wire up the switch.
So what I did there was take a red wire and I went up to the center terminals, the two
center terminals and put the red wire between those.
So that's going to be nine volts power going up to the center of the switch but it's
not doing anything at that point.
If I pull down it's going to make momentary contact and I think I had a yellow wire,
yeah I think it was yellow, a yellow wire went out and that's what's going to pull it,
charge up the capacitor to pull in the MOSFET.
If I pushed up, I had to go to another color wire I can't remember now but it's probably
going to be in the show notes.
If I pushed up, that was a maintained contact pushing up and I just had a wire go from
that terminal down to the terminal that was momentary already.
So I'm not sure if that's making any sense but in the up position it's maintained and
I just went down to the momentary contact just so I can use that yellow wire again.
I wouldn't have to have two wires running through the board and then down momentary that's
going to charge the yellow wire up just for a second and those two won't interfere
with each other.
They'll just, one will send nine volts up to the other and I won't do anything with
it.
So this all worked out well and it reduced the amount of wires I had inside the meter.
After that was done, it was just a matter of putting it all in the meter.
I secured the component board into the back of the meter with a little bit of hot glue.
I screwed the switch on and I have it in my hand right now and you pull down and it turns
on.
It runs for five minutes like I told you I changed the timing on and if I push the
switch up it's maintained so I could use that data logging feature of this meter or if
I just need to have the, sometimes on the bench, I just leave my meters run with the
power supply, just turn everything on, I do whatever I'm doing but it's when I leave
the house with one of these meters that I would turn it on, do something at the lug
or the 2600 meeting and then get distracted and throw the thing aside and forget that
I just left it on and it sits in my bag for like a week or a month and the battery is
dead by the next time I use it.
So now my modifications are complete, there's part two, I have this Unity UT61E which I actually
did a review of, you might have heard that before you hear this one.
This has become my favorite electronics meter, I use this all the time and if you heard
the last one I've actually purchased the second one so I'm kind of a meter nut and now
I have the backlight that I want in it and now I have the auto timeout feature so I'm
happy if you don't like it, hack it, okay so guys if anybody wants to leave comments
in the comment section or email is nybill at gunmunkinette.net and status net gnusoscial
is sn.gunmunkinette.net, okay I'll talk to you guys later.
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