hpr-knowledge-base/hpr_transcripts/hpr0772.txt

Episode: 772
Title: HPR0772: Circuit Bending
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr0772/hpr0772.mp3
Transcribed: 2025-10-08 02:09:52

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MUSIC
Welcome HPR listeners to my new show this is the new age techno hippie I'm going to talk
about circuit bending today it was a topic that I didn't even know was a topic I had started
doing similar types stuff a while ago after I had my children and found out that a lot
of the toys today don't come with volume control so I wanted to lower the volume but couldn't
so being a hacker I just decided I was going to put one in myself it's not that complicated
of a subject but I'm going to have some links in the show notes to actual circuit bending
websites and you check it out they seem to do a little bit different than what I'm doing
I'm basically just adding in volume control they're going a little bit further than that
but once you start I'm sure that you could with enough time do about anything you want
it the concept is pretty simple I have a child's toy and it has no volume control so what
am I going to do I'm going to take a screwdriver or whatever tools that I need and I'm going
to take the device apart sometimes screws are hidden under rubber feet on the back you
take those off and you'll see the screw holes you stick your screwdriver in there they might
be Phillips they might be straight edge not normally most of the time they're Phillips
or sometimes some sort of torque said maybe a try wing there's all sorts of screws out
there if you look online I'm sure you can figure out what kind of screwdriver you'll need
once you have the screws out then you slowly take the toy apart be careful plastic breaks
easy most of the toys are made out cheap plastic and they have lots of little fasteners normally
I use a little precision straight edge screwdriver and you can slowly pop all the little plastic
bits apart once you have a plastic bits apart then you just time to start dealing with the
electronics inside most of these have one to two small circuit boards in them with a lot of
integrated circuit but for the volume out you're going to have some sort of audio circuit and that
audio circuits where we're going to do our work to add a volume control to it it's not super
straight forward if you look out there online for filters for audio circuit simple filters you'll
see that all you really need to change the sound of audio is some resistors maybe a capacitor
and you can wind up changing the pitch and volume of audio pretty easy problem is somebody's already
done a lot of design work to get this toy to sound exactly the way they wanted and you're going
to be changing that so you're going to have to experiment a little bit but it doesn't really
all you need to do is just leave the batteries in the toy take the toy apart leave the speaker
connected and you can hear the speaker and run it through its actions and the different sounds
that it makes and then you can go in and put a volume control of your own in that toy or just
lower the volume altogether not even really put a control and just cut the volume in half or
something so what you're going to do is you're going to have two options here you could get really
fancy because you already have a screwdriver you can do it really fancy and you can do use a soldering
iron and desolder the wires from the speaker off the board and use a resistor or a variable resistor
in there and play with the volume that way or you can just simply if you don't have a soldering
iron just cut one of the wires to the speaker normally the red one the one that looks like it's
the positive wire might even be labeled positive on the on the board circuit board where the wires
attach from the speaker if you cut that wire you can put a resistor in between the wire and the
speaker and by doing that you're going to reduce the voltage across the speaker and that's going
to reduce the volume that comes out of the speaker you also play down with different resistor values
you can buy a cheap pack of variable resistor or variable resistors or even just a cheap pack with
a lot of different resistors in it and a lot of different values from any hobby electronics store
whether it's a radio shack or whatever else you might have maplin whatever when you do that then
you can try different resistors in there just by simply touching them together you can use them
if you need to hold a little bit of tape to them together or just hook the little ends of the wire
and the resistor wires and hook them together and just kind of tug on it gently generally you're not
talking enough voltage or amperage or anything that you're going to get hurt playing around with
these kinds of circuits if you're dealing with some kind of electronic item that's a lot bigger
or plugged into AC power you need to be very careful and that you don't you know shock yourself but
with small you know double way battery single double way battery type toys double two double
way batteries generally not too big a problem there I'm trying not to touch the bear wires
but there's lots of ways to hold these things apart so as you're trying to different resistor values
you just turn the toy on cycle it through its different functions and make sure that the volume
level is the volume level that you wanted to have for the toy and once you find the right
resistor value the toy should still sound good but yet just be at a lower volume as you change
the resistor value you might find that you change the sound of whatever is coming out whether it's
a voice or just a pitch you're going to change that slightly by changing the resistor value and
that goes back to what I said earlier about there being a lot of work going into designing the
audio circuit to sound a certain way and now you're just sort of going in and changing it all random
like but with a little bit of work you can get the right resistor in there and that resistor will
make what you have sound good but be at a volume that you prefer if you put a variable resistor in
you'll have the option of changing it now if you want to access the variable resistor after
you put this toy back together you might need to poke a small hole through the toy to do so you
can use a knife and just auger out a hole or if you want you can use a drill or something like that
poke a little hole in it that way just big enough to get a small little precision screwdriver
through there and that's normally enough that you can glue the resistor that you're going to add
to it the variable resistor into the toy and be able to turn the little potentiometer there
with a screwdriver to change the volume whenever you want it once you find the resistor if you don't
have a soldering iron you can just twist the wires together tape everything up and you put the toy
back together don't put screws in test it out first before you put the screws back in make sure
everything works the way you want and then you're ready to go then you put screws back in if you
have a soldering iron what you can do is you can solder the resistor in place and then put the toy
back together test it out put the screws in if everything's working the way you want if you put a
variable resistor in there until potentiometer and you glued it to the hole then put it back to
solder everything back in together normally with the variable potentiometer you're going to have
the solder stuff just because of the way that the mounts are made sometimes you might not have to
you might be able to tape them together soldering is obviously a little bit more secure it's going to
harden everything up solder psych welding for electronics if you don't know what that is already
you know we'll be a little bit more solid if you just tape it up it might be a little less solid
but generally I've had good luck with both methods before depending on how many tools I've had
available when I've done it once you get everything back together it should be good to go and you
can put the screws back in there if everything's working the way you expect and you'll be happy with
your new volume and most of the time your kid will not even notice I've done this to a lot of my
child's toys and my spouse has been very happy because of it so there's a lot further that you can
go if you check out the show notes you'll see some of the circuit bending websites and that'll get
you into a deeper world of how to modify toys or electronics in general so have a good day talk to you
next time
thank you for listening to Hacker Public Radio for more information on the show and how to
contribute your own shows visit Hacker Public Radio dot org
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