Episode: 2924
Title: HPR2924: Hacking an Alarm Clock to Make it Quieter
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr2924/hpr2924.mp3
Transcribed: 2025-10-24 13:20:05

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It's the 17th of October 2019 and this is HBR episode 2924 entitled Hacking in a Larm
Clock to Make It quieter. It's hosted by John Colp and it's about six minutes long carrying
a clean flag. Some areas. I talk about installing a resistor in the speaker wire of an alarm
clock so it won't be so loud. Enjoy!
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Hey everybody this is John Colp and left here at Louisiana and this probably be a pretty quick
episode today. What I wanted to talk about was a recent hack I did on a small device in my house.
It is a little just alarm clock a little digital alarm clock by Sharp. It's something I picked up
at the thrift store for a couple of bucks probably for I don't even remember why because I had a
clock radio at the time but somebody in the house must have needed a little alarm clock and so
I picked it up and it does not have a radio or anything it just does one thing it tells the time
and then it will do an alarm also and it's the alarm that brings me to where we are today making
an episode about this. I normally use an alarm on my phone to wake up in the morning if I need any
alarm at all. I usually will wake up before the alarm goes off anyway but you know I like retro
things and old school stuff and so one day this last week I decided you know what I'm going to
just set the alarm on this little bedside alarm clock because I got rid of my clock radio because
I didn't like it was there was something going wrong with it like the the outside casing was
getting all sticky and I didn't want to it's just I got rid of it and then so now all I've got
next to the bed is this little clock with no radio but I decided one day last week to set the alarm
on the clock and go old school and just have an alarm clock wake me up well next morning when the
alarm went off it was so loud that I sat straight up in bed with my heart pounding and it really
scared me and it scared my wife and you know it was not a good thing and so I started thinking what
I could do possibly to make it quieter and I started googling online about how to
make the alarm clock quieter and I came across an article or a little blog post or something that
that someone had written about making one of your children's toys quieter by simply inserting a
resistor in one of the speaker wires and I thought well that sounds easy enough I'm going to try
that with this alarm clock as well but I didn't really know what the alarm clock had inside it whether
it had a speaker or a buzzer or what so I opened the thing up and found that I've got some pictures
that I will make a flicker album right now I'm looking at them on my tablet but inside the alarm
clock it's very small there's a little transformer for the power to get it down to the right
voltage and then there's a small circuit board there's a little LED read out I guess for the numbers
and then in the bottom of the case there's a round thing with two wires soldered directly to it it
looks like it's a buzzer I don't think it's an actual speaker but I guess it could be I can't see
the underside of it but anyway it's the thing that makes the noise and so it was right there
and it seemed very easy to be able to just cut one of those wires and stick a resistor in there so
I did that and it didn't make a noticeable difference I the first resistor I used I think was
not nearly enough resistance and I'm very sorry that I did not record the sound of the alarm
clock before and after because that would have made a better impression as to you know what a
difference the resistors make but anyway the first resistor I tried did not make a substantial
difference it did not noticeable at all to me I think I went with something like a 256 ohm or two
whatever something in that range and so I decided to cut the other speaker wire to put another
resistor in that one rather than undoing the one I had already done because I had already done the
heat shrink on the wires and everything so anyway before I soldered in the other resistor I started
testing it by I made the alarm clock go off and just left it go left the alarm going and then
just one by one I tried one resistor after another in increasing strength and you know put the
connectors put the put the I guess the the leads or connections together to listen to the sound
and I finally found one that sounded like it reduced the sound enough where it wouldn't scare
me to death in the morning but also it would wake me up and it was the 12k ohms so 12 like
it's 12,000 ohms 12k ohm resistor soldered into place there made the alarm clock where it was
tolerable but also would still wake me up so I'm pretty happy with it I'm the the wife is still not
crazy about the sound of it I think she likes the sound of the phone going off better but it was
a pretty fun little hack it didn't take all that long and you know it's always satisfying when
you can modify one of the items in your house to make it work more like you wanted to and so I
certainly encourage anybody who's got an alarm clock that's too loud that they would like to use
and have some resistors lying around I mean I have a I bought on Amazon a kit of resistors I think
it's got I don't know 1200 different resistors in it of all levels of resistance so you know
anytime I need a resistor I can just dig around in there and find one it may be cost ten dollars
to get the kit of 1200 resistors and so it's it's easy enough to keep these kinds of things around
if you're interested in doing these sorts of projects anyway so if you're interested take a look
on my flicker photo album you can see the pictures of the inside of the thing and then what it
looks like after it's done well it's just a closed up alarm clock flashing the number 12 but um
that's it that that's all I got today this is not a long episode at all I will uh talk to you guys
next time okay bye
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