A noob question about pots and their value/use.



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A noob question about pots and their value/use.

Postby Confuzzled » Fri Nov 03, 2017 10:34 am

I have a lot of pots from my old job that were given to me and lots of components from my off and on again circuit bending experiments over the years. As I've said in the past I know jack shit about electronics and stick with battery operated tinkering to avoid winding up in the ER.

I finally got myself a multimeter and put a bunch of pots on there to test their resistance. and I have a few that I brought with me that are 2k and a few that came up as 43k? Does that sound right?

Anyway, I picked this up at home depot on clearance:

https://www.homedepot.com/p/Home-Accent ... /301148798

Makes a kick as buzzing light up oscillating sound and I wanted to try to take them apart and re-wire them so that each one I can vary the pitch and figure out a way to keep them on indefinitely with a switch.

My question is, would I be wiring a pot to each to vary the resistance which would change the pitch? How would I know which value pot to use? This runs on batteries and has a speaker(s) so putting it in an enclosure and output jack I can handle. The rest should be interesting.

Any help or advice would be appreciated.
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Re: A noob question about pots and their value/use.

Postby BetterOffShred » Fri Nov 03, 2017 10:56 am

All elements that consume current need a load so if you do go messing with it make sure you series in like a 100R to each so they don't pop on you.

Without a schematic it's hard to tell what changing stuff out will do, but I'd wager a guess that lowering the voltage may change the pitch of your oscillation. . It may stop it entirely.

What are the markings on the pots? Usually they have a sweep type followed by max value. So like A100k. Is an audio taper pot with a max value of 100k.. audio taper is also called logarithmic, a quick Google search will show you the tapers if you're unfamiliar.

If I'm testing something and I don't know what to expect, I'll typically start with a linear taper B pot.

Old Ohms law should put you in the ballpark for a min resistor value
. E=I*R. So if they are running on 12v and you want them to pull 20ma .. 12/0.020 = 600R. So toss a 1k in there and see what happens with like a 10k pot. It's also been my experience that water clear LED are blinding at 20ma.. I run mine at like 2ma. Usually a 5.6k or 6.8k resistor with a 9v supply.

Once again make sure to have a 100R or something in series with either side of the pot to give a minimum load so you don't pop them LEDs. (Or higher)

Have fun and let us know what you come up with :)
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Re: A noob question about pots and their value/use.

Postby Confuzzled » Fri Nov 03, 2017 11:07 am

some say 50kA one says 1C one says 5F1 B2k?

So start with 100k pots to test? I was watching videos this morning where folks tested the two utter lugs for overall resistance and then the left and center lug. I still have to open these up and figure out where the pots would even connect to! :D
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Re: A noob question about pots and their value/use.

Postby BetterOffShred » Fri Nov 03, 2017 11:11 am

It's literally a little wafer in there and as you use a longer piece of it, the resistance goes up. So for a variable resistor configuration you just use one end and the middle. Throw it on the meter and test it both ways. One way will make turning the pot "up" raise resistance where the other side will make it lower. Yeah 100k is a safe starting point. Put a 1k in series through it and go to town. CAUTION I would measure the voltage going through the LEDs first and also see where it's converting to DC.. you don't want to go messing with AC if you're not prepared..
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Re: A noob question about pots and their value/use.

Postby crochambeau » Fri Nov 03, 2017 11:12 am

All electronic parts have a tolerance, so values above or below the printed value are normal. It is not unusual for a pot to have a +/- 20% tolerance, indicating what you measure at 43K was probably sold as a 50K. There will probably be some numbers printed on the pot to confirm or dispute that statement... look for them, familiarization with parts codes is useful (though measuring is far more precise).

Without a schematic I cannot indicate how best to exploit pots in your light string, but there are two methods in common use:

1) Voltage divider (potentiometer) in which all three legs of the part are used. Often (but not always) with your "high" voltage or signal source on one outer, the reference or "ground" on the other outer, and the variable output on center wiper.

2) Variable resistance (rheostat) in which one outer leg is tied to the center wiper and the part is considered a two leg system that replaces a fixed resistor.

If you're just blindly poking around, I would start with option 2 and move on to option 1 if option 2 is not providing satisfactory results.

(edit) BoS gives good advice regarding including a series resistor. It takes me a long time to type shit out when helping a kid get ready for school, hahaha)
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Re: A noob question about pots and their value/use.

Postby Confuzzled » Fri Nov 03, 2017 11:41 am

BetterOffShred wrote:It's literally a little wafer in there and as you use a longer piece of it, the resistance goes up. So for a variable resistor configuration you just use one end and the middle. Throw it on the meter and test it both ways. One way will make turning the pot "up" raise resistance where the other side will make it lower. Yeah 100k is a safe starting point. Put a 1k in series through it and go to town. CAUTION I would measure the voltage going through the LEDs first and also see where it's converting to DC.. you don't want to go messing with AC if you're not prepared..


Ok this I can follow (I think)... put the meter on the LED and see what the voltage is? Not sure how to figure out where the DC is converting. so once I get the voltage reading how do I determine what the resistance on the pot should be?

Essentially I'm looking to alter the sound of each unit and get it to stay on (currently they are motion activated when someone walks past them) and put them in an enclosure.
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Re: A noob question about pots and their value/use.

Postby Confuzzled » Fri Nov 03, 2017 11:51 am

crochambeau wrote:All electronic parts have a tolerance, so values above or below the printed value are normal. It is not unusual for a pot to have a +/- 20% tolerance, indicating what you measure at 43K was probably sold as a 50K. There will probably be some numbers printed on the pot to confirm or dispute that statement... look for them, familiarization with parts codes is useful (though measuring is far more precise).

Without a schematic I cannot indicate how best to exploit pots in your light string, but there are two methods in common use:

1) Voltage divider (potentiometer) in which all three legs of the part are used. Often (but not always) with your "high" voltage or signal source on one outer, the reference or "ground" on the other outer, and the variable output on center wiper.

2) Variable resistance (rheostat) in which one outer leg is tied to the center wiper and the part is considered a two leg system that replaces a fixed resistor.

If you're just blindly poking around, I would start with option 2 and move on to option 1 if option 2 is not providing satisfactory results.

(edit) BoS gives good advice regarding including a series resistor. It takes me a long time to type shit out when helping a kid get ready for school, hahaha)


I wish there was a video on how these things sound, I'm going to have to post something on IG and when I open them up I'll post some gutshots here.
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Re: A noob question about pots and their value/use.

Postby BetterOffShred » Fri Nov 03, 2017 11:58 am

LED is a diode as the name indicates so it won't be using AC or they would have 60 cycle blinking, because current only flows one way through them, so as the AC wave cycled directions it would be blocked causing the led to flicker. So they will have a transformer device in there somewhere taking the wall power (I assume it has a 120v plug) through some windings and then out the other side through some sort of diode rectification with some caps for riple filtering. Once you're certain you're nowhere near the AC put your meter on one side of the LED and the other part where they all connect back to the diode rectifiers.. I know that sounds bad it's hard to explain. If you have an old cell phone charger you can sacrifice, pull it apart so you can see where the voltages are what with these little transformers

The motion sensor part will just be a sensor with a timer on a little board with the power going through it. Delete this board and you hook the power up straight through. (Maybe an on off switch)

Using a meter on both sides of the LED will only tell you what the voltage drop through the component is. Not what the base voltage supply is.
So if you ran a 9v battery through 2 resistors, and put your meter on the first, it would read just what the drop across that resistor is, but if you put one mead at the + end of the first resistor and then the other after the second resistor it would read 9v because those 2 resistors "used" up the 9v. As there is no other components.

So you have to find where the DC comes out to see what they are running it at
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Re: A noob question about pots and their value/use.

Postby crochambeau » Fri Nov 03, 2017 1:25 pm

There will probably be a 1-3 volt drop across the LEDs, and as stated above it is an unimportant number. What *is* important is limiting current through the LED, as they will die if exposed to an over current and they have no protection aside from a resistor.

I just mention this because it would be easy to shunt that load resistor with option #2 I described above and allow the LED to OD on juice.

To dabble you want to dick around with stuff in the controller, which is probably just a tiny micro-controller possibly under a bead of epoxy.

Taking stuff apart and putting it back together is good practice anyway.
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Re: A noob question about pots and their value/use.

Postby Confuzzled » Fri Nov 03, 2017 2:48 pm

BetterOffShred wrote:LED is a diode as the name indicates so it won't be using AC or they would have 60 cycle blinking, because current only flows one way through them, so as the AC wave cycled directions it would be blocked causing the led to flicker. So they will have a transformer device in there somewhere taking the wall power (I assume it has a 120v plug) through some windings and then out the other side through some sort of diode rectification with some caps for riple filtering. Once you're certain you're nowhere near the AC put your meter on one side of the LED and the other part where they all connect back to the diode rectifiers.. I know that sounds bad it's hard to explain. If you have an old cell phone charger you can sacrifice, pull it apart so you can see where the voltages are what with these little transformers

The motion sensor part will just be a sensor with a timer on a little board with the power going through it. Delete this board and you hook the power up straight through. (Maybe an on off switch)

Using a meter on both sides of the LED will only tell you what the voltage drop through the component is. Not what the base voltage supply is.
So if you ran a 9v battery through 2 resistors, and put your meter on the first, it would read just what the drop across that resistor is, but if you put one mead at the + end of the first resistor and then the other after the second resistor it would read 9v because those 2 resistors "used" up the 9v. As there is no other components.

So you have to find where the DC comes out to see what they are running it at


No plug! I'm not that nuts! It runs on 3 AA batteries I believe.
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Re: A noob question about pots and their value/use.

Postby BetterOffShred » Fri Nov 03, 2017 3:24 pm

Oh well hell then have at it. That's 3.6v.
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Re: A noob question about pots and their value/use.

Postby eatyourguitar » Thu Nov 09, 2017 1:57 pm

BetterOffShred wrote:Oh well hell then have at it. That's 3.6v.

any AA or AAA is spec for 1.5v so three of them is spec for 4.5v. the device itself is spec for either 3v or 3.3v operation to prevent failure on a half dead battery. it can be safely powered from a boss style 9.5v power connector if you put two of them in series = 4.75v each. you can also put 3 in series for 3.1333v each. after that, you can add chains of 3 or chains of 2 in parallel.

@ OP how are you getting sounds out of a light that is just a light? is this a bug turned into a feature?
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