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Magnets & Copper Wire: A Pickup Building Thread
- Thread starter Freekmagnet
- Start date
Pretty sure you can use an oscilloscope to measure inductance - not exactly sure how, but something do with phase shift?
Edit: Found this...
I am aware.
I'm also pretty sure my rigol can make toast. I still prefer my toaster though as it's more efficient and in times of being really thorough I can actually toast my toast with both to ensure a more accurate toasting.
Hopefully that's not too crass and makes sense lol.LMAO!!!I am aware.
I'm also pretty sure my rigol can make toast. I still prefer my toaster though as it's more efficient and in times of being really thorough I can actually toast my toast with both to ensure a more accurate toasting.
I always thought those were height adjustment screws like on a dynasonic/staple! (I've never seen one of those in real life)
Ok, so about that measurement... Had a group of rather "wild" students at the workshop today, so I couldn't get the best setup and results, but here goes...
I'll try to keep the theory to a minimum. So first of, since the pickup is basically an inductor, it has the same electrical properties - the main parameter, inductance, some series resistance, and parasitic capacitance.
This would be an equivalent schematic of an inductor:
This is basically a lossy parallel resonant tank circuit. If this were placed as a LC tank in an oscillator, the circuit would oscillate at the resonant frequency.
So we just need to make it oscillate for enough time to measure the frequency of oscillations. If this coil were to be excited by a voltage impulse, it would have a short unsustained oscillation.
To do this, we can apply a square wave signal to the coil, and the measure the result.
Here is the setup:
The diode is needed to help increase the oscillations, and R3 is used to reduce the current drawn form the generator. In my experiments, around 10× the resistance of the pickup worked. And the signal from the generator should be lower than the expected value of the resonant frequency. These are purely experimental values, so you might need some tinkering with them - for example I never managed to get some chokes to oscillate at all
The output should look something like this:
As can be seen, the green output signal has ringing on it. The frequency of that ringing is the resonant frequency of the pickup. An that is something that can be measured wit an oscilloscope.
Enough about theory, here are some pics from my measurement:
This is a coil that I made for my multi coil pickup project (which I will hopefully finish one day
) R=1KOhm, 6000 turns of AWG43 wire.
And here are the results:
Yellow is the input signal. Blue is the measured signal. As you can see the oscilloscope tries to measure the frequency, but this is better done by using cursors or manually calculating when zoomed in:
Here you can see that the resonant frequency of my coil is around 40kHz.
Fun fact, here is the same measurement when I put in a steel pole piece:
As you can see, the addition of an iron core increases the inductance, which in turn lowers the resonant frequency...
Conclusions:
This would be the short butchered version of how to do it....
I just got an idea, that reversing the diode might result in a cleaner output waveform, so I'll check that tomorrow and post if it looks easier to read.
Also, I'll try to find a proper pickup and see what results I get...
Hope this was helpful!
I'll try to keep the theory to a minimum. So first of, since the pickup is basically an inductor, it has the same electrical properties - the main parameter, inductance, some series resistance, and parasitic capacitance.
This would be an equivalent schematic of an inductor:
This is basically a lossy parallel resonant tank circuit. If this were placed as a LC tank in an oscillator, the circuit would oscillate at the resonant frequency.
So we just need to make it oscillate for enough time to measure the frequency of oscillations. If this coil were to be excited by a voltage impulse, it would have a short unsustained oscillation.
To do this, we can apply a square wave signal to the coil, and the measure the result.
Here is the setup:
The diode is needed to help increase the oscillations, and R3 is used to reduce the current drawn form the generator. In my experiments, around 10× the resistance of the pickup worked. And the signal from the generator should be lower than the expected value of the resonant frequency. These are purely experimental values, so you might need some tinkering with them - for example I never managed to get some chokes to oscillate at all
The output should look something like this:
As can be seen, the green output signal has ringing on it. The frequency of that ringing is the resonant frequency of the pickup. An that is something that can be measured wit an oscilloscope.
Enough about theory, here are some pics from my measurement:
This is a coil that I made for my multi coil pickup project (which I will hopefully finish one day
) R=1KOhm, 6000 turns of AWG43 wire.And here are the results:
Yellow is the input signal. Blue is the measured signal. As you can see the oscilloscope tries to measure the frequency, but this is better done by using cursors or manually calculating when zoomed in:
Here you can see that the resonant frequency of my coil is around 40kHz.
Fun fact, here is the same measurement when I put in a steel pole piece:
As you can see, the addition of an iron core increases the inductance, which in turn lowers the resonant frequency...
Conclusions:
This would be the short butchered version of how to do it....
I just got an idea, that reversing the diode might result in a cleaner output waveform, so I'll check that tomorrow and post if it looks easier to read.
Also, I'll try to find a proper pickup and see what results I get...
Hope this was helpful!
Attachments
Very interesting, thanks.Ok, so about that measurement... Had a group of rather "wild" students at the workshop today, so I couldn't get the best setup and results, but here goes...
I'll try to keep the theory to a minimum. So first of, since the pickup is basically an inductor, it has the same electrical properties - the main parameter, inductance, some series resistance, and parasitic capacitance.
This would be an equivalent schematic of an inductor:
View attachment 4842750
This is basically a lossy parallel resonant tank circuit. If this were placed as a LC tank in an oscillator, the circuit would oscillate at the resonant frequency.
So we just need to make it oscillate for enough time to measure the frequency of oscillations. If this coil were to be excited by a voltage impulse, it would have a short unsustained oscillation.
To do this, we can apply a square wave signal to the coil, and the measure the result.
Here is the setup:
View attachment 4842765
The diode is needed to help increase the oscillations, and R3 is used to reduce the current drawn form the generator. In my experiments, around 10× the resistance of the pickup worked. And the signal from the generator should be lower than the expected value of the resonant frequency. These are purely experimental values, so you might need some tinkering with them - for example I never managed to get some chokes to oscillate at all
The output should look something like this:
View attachment 4842768
As can be seen, the green output signal has ringing on it. The frequency of that ringing is the resonant frequency of the pickup. An that is something that can be measured wit an oscilloscope.
Enough about theory, here are some pics from my measurement:
View attachment 4842776
This is a coil that I made for my multi coil pickup project (which I will hopefully finish one day
And here are the results:
View attachment 4842781
Yellow is the input signal. Blue is the measured signal. As you can see the oscilloscope tries to measure the frequency, but this is better done by using cursors or manually calculating when zoomed in:
View attachment 4842786
Here you can see that the resonant frequency of my coil is around 40kHz.
Fun fact, here is the same measurement when I put in a steel pole piece:
View attachment 4842787
As you can see, the addition of an iron core increases the inductance, which in turn lowers the resonant frequency...
Conclusions:
This would be the short butchered version of how to do it....
I just got an idea, that reversing the diode might result in a cleaner output waveform, so I'll check that tomorrow and post if it looks easier to read.
Also, I'll try to find a proper pickup and see what results I get...
Hope this was helpful!
Love love love this! Gonna try it tomorrow! Seems like the only areas that may need playing with is R3 and that 1n914, might need to dig out my sub box, dunno. I really like your suggestion of using the cursors to measure I think I've only played with that once on this scope and it hadn't occurred to me lol.Ok, so about that measurement... Had a group of rather "wild" students at the workshop today, so I couldn't get the best setup and results, but here goes...
I'll try to keep the theory to a minimum. So first of, since the pickup is basically an inductor, it has the same electrical properties - the main parameter, inductance, some series resistance, and parasitic capacitance.
This would be an equivalent schematic of an inductor:
View attachment 4842750
This is basically a lossy parallel resonant tank circuit. If this were placed as a LC tank in an oscillator, the circuit would oscillate at the resonant frequency.
So we just need to make it oscillate for enough time to measure the frequency of oscillations. If this coil were to be excited by a voltage impulse, it would have a short unsustained oscillation.
To do this, we can apply a square wave signal to the coil, and the measure the result.
Here is the setup:
View attachment 4842765
The diode is needed to help increase the oscillations, and R3 is used to reduce the current drawn form the generator. In my experiments, around 10× the resistance of the pickup worked. And the signal from the generator should be lower than the expected value of the resonant frequency. These are purely experimental values, so you might need some tinkering with them - for example I never managed to get some chokes to oscillate at all
The output should look something like this:
View attachment 4842768
As can be seen, the green output signal has ringing on it. The frequency of that ringing is the resonant frequency of the pickup. An that is something that can be measured wit an oscilloscope.
Enough about theory, here are some pics from my measurement:
View attachment 4842776
This is a coil that I made for my multi coil pickup project (which I will hopefully finish one day
And here are the results:
View attachment 4842781
Yellow is the input signal. Blue is the measured signal. As you can see the oscilloscope tries to measure the frequency, but this is better done by using cursors or manually calculating when zoomed in:
View attachment 4842786
Here you can see that the resonant frequency of my coil is around 40kHz.
Fun fact, here is the same measurement when I put in a steel pole piece:
View attachment 4842787
As you can see, the addition of an iron core increases the inductance, which in turn lowers the resonant frequency...
Conclusions:
This would be the short butchered version of how to do it....
I just got an idea, that reversing the diode might result in a cleaner output waveform, so I'll check that tomorrow and post if it looks easier to read.
Also, I'll try to find a proper pickup and see what results I get...
Hope this was helpful!
Seriously cool stuff man I'm sure this will help more than a few folks in this thread too so thank you, you rock!
I've been experimenting with coils in different configurations looking for a single coil tone with hum cancelling. In previous posts I've spoken about sidewinder pickups. Today I built two identical single coils and wired one into each of the inverting and non inverting inputs on my pre amp. With the magnet in one coil only, I get a good single coil tone and no hum. With the dummy coil removed I get the same tone with hum. It makes me wonder, what is the advantage of a sidewinder if the dummy coil cancels hum without changing the tone?
While I was at it, I put steel rails in both coils and bridged them with a bar magnet, then lifted the magnet so it only touched 1 rail. It switched from a humbucker tone to a single coil tone. The difference was small though. I'm thinking about putting 3 coils in there. I'd keep one connected permanently and switch between the other 2, so that I can switch between humbucker and noiseless single. There isn't room for 3 conventionally shaped coils, but I could fit a flat-but-wide coil in under the other two. Does the shape of a noise cancelling coil affect its noise cancelling?
People have different goals for their tone, and for some of them a sidewinder makes the sound they want.
Aside from that, take a look at Alembic's electronics. Dummy coils have been a standard component from the beginning. iirc, since a dummy doesn't have magnets it can't sense string movement so hypothetically you could put it anywhere in the instrument. It might not have to be in a pickup position.
If I recall correctly, the amount of noise a coil picks up is proportional to the area inside the coil times the number of turns. So you can change the shape then tweak the number of turns to get back to the same performance.
How would you wire this pickup together? I have 3 coils. Two that form a humbucker and a third with no magnet. I want to switch out one of the humbucker coils for the magnetless coil on the fly, to switch between noiseless singe and humbucker tones.
I've currently got them wired like this. If the switch is connected from the midpoint to ground it works well. If connected from the midpoint to the input it hums like a single coil. I can swap L1 and L3 and the noise remains with the upper position. Remove the third coil and the circuit works really well as either a humbucker or a noiseless single.
The reason I went for shorting out one or other coil is so that the amplifier input is never open circuit while moving between the two positions. That would be bad. What other switching should I try?
I've currently got them wired like this. If the switch is connected from the midpoint to ground it works well. If connected from the midpoint to the input it hums like a single coil. I can swap L1 and L3 and the noise remains with the upper position. Remove the third coil and the circuit works really well as either a humbucker or a noiseless single.
The reason I went for shorting out one or other coil is so that the amplifier input is never open circuit while moving between the two positions. That would be bad. What other switching should I try?
Is your diagram correct? If I understand this correctly (I am very much a newbie w/r/t circuitry) it looks like whichever way the switch is thrown both L1 and L3 remain in circuit. L1 generates current (when the guitar strings move) so it won't be shorted regardless of switch position, you're only providing an optional route around L3 when the switch is up rather than down.
When you say "remove" do you mean make it an open circuit? If so, that would result in only L2 and the non-inverting side would be open when the switch was in the down position.
If that's not it can you explain in more detail?
When the switch is down, L1 is shorted out, so L3 is connected from ground to the input.
When the switch is up, L3 is shorted out, so L1 is connected from ground to the input.
The idea is that L2 is always connected, either L1 or L3 is connected to the other input and at no time while switching is there an open circuit.
When the switch is up, L3 is shorted out, so L1 is connected from ground to the input.
The idea is that L2 is always connected, either L1 or L3 is connected to the other input and at no time while switching is there an open circuit.
OK, I though you might have meant specifically L3 when you said 3rd coil.
Either way, shorting out a coil is electrically the same as it not being there, so if manually rewiring gives different results than using the switch either you have a bad switch or things aren't wired like you planned. You can use an ohm meter to confirm that the switch is really shorting one of the coils.
Your schematic looks correct to me (as it pertains to the coil switching part).
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