I can build this into my new programmable inductor module, for
self-test. With a 1% cap, it should be plenty good. L range will be
750 mH down to maybe 10 mH, part of simulating solenoids and torque
motors and such.

If I add a switch to open R3 and run some current through R1, it can
measure series resistance too.

https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1

https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0

On Mon, 08 Apr 2024 17:17:15 -0700, john larkin <jl@650pot.com> wrote:

>I can build this into my new programmable inductor module, for
>self-test. With a 1% cap, it should be plenty good. L range will be
>750 mH down to maybe 10 mH, part of simulating solenoids and torque
>motors and such.
>
>If I add a switch to open R3 and run some current through R1, it can
>measure series resistance too.
>
>https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>
>https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0

Most L-meters, the AADE sort, lie or don't work with big Ls.

This is better:

https://www.dropbox.com/scl/fi/9tex1slpnaqz4n2cbxp3n/Ind_Meter_Apr_9.jpg?rlkey=52vbyylc5ax48w54qdxm9r9cq&raw=1

Given a small uP, like the Rasp Pi thing, it could measure L and Rl
pretty easily. One could get compusive and math out the small
inductance measuring error from the inductor copper resistance.

I need repeatability more than accuracy, and don't have time to
explore this very deep, but it's interesting.

I've been buying shaftless torque motors off ebay, to understand them
electrically. We need to simulate a torque motor.

On 4/9/24 16:19, John Larkin wrote:
> On Mon, 08 Apr 2024 17:17:15 -0700, john larkin <jl@650pot.com> wrote:
>
>> I can build this into my new programmable inductor module, for
>> self-test. With a 1% cap, it should be plenty good. L range will be
>> 750 mH down to maybe 10 mH, part of simulating solenoids and torque
>> motors and such.
>>
>> If I add a switch to open R3 and run some current through R1, it can
>> measure series resistance too.
>>
>> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>>
>> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0
>
> Most L-meters, the AADE sort, lie or don't work with big Ls.
>
> This is better:
>
> https://www.dropbox.com/scl/fi/9tex1slpnaqz4n2cbxp3n/Ind_Meter_Apr_9.jpg?rlkey=52vbyylc5ax48w54qdxm9r9cq&raw=1
>
> Given a small uP, like the Rasp Pi thing, it could measure L and Rl
> pretty easily. One could get compusive and math out the small
> inductance measuring error from the inductor copper resistance.
>
> I need repeatability more than accuracy, and don't have time to
> explore this very deep, but it's interesting.
>
> I've been buying shaftless torque motors off ebay, to understand them
> electrically. We need to simulate a torque motor.
>
>

What's R1 (1G to +5) for?

Are torque motors actually predominantly inductive? Just
because it has coils doesn't necessarily mean it is so.

Jeroen Belleman

On Tue, 9 Apr 2024 17:36:28 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

>On 4/9/24 16:19, John Larkin wrote:
>> On Mon, 08 Apr 2024 17:17:15 -0700, john larkin <jl@650pot.com> wrote:
>>
>>> I can build this into my new programmable inductor module, for
>>> self-test. With a 1% cap, it should be plenty good. L range will be
>>> 750 mH down to maybe 10 mH, part of simulating solenoids and torque
>>> motors and such.
>>>
>>> If I add a switch to open R3 and run some current through R1, it can
>>> measure series resistance too.
>>>
>>> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>>>
>>> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0
>>
>> Most L-meters, the AADE sort, lie or don't work with big Ls.
>>
>> This is better:
>>
>> https://www.dropbox.com/scl/fi/9tex1slpnaqz4n2cbxp3n/Ind_Meter_Apr_9.jpg?rlkey=52vbyylc5ax48w54qdxm9r9cq&raw=1
>>
>> Given a small uP, like the Rasp Pi thing, it could measure L and Rl
>> pretty easily. One could get compusive and math out the small
>> inductance measuring error from the inductor copper resistance.
>>
>> I need repeatability more than accuracy, and don't have time to
>> explore this very deep, but it's interesting.
>>
>> I've been buying shaftless torque motors off ebay, to understand them
>> electrically. We need to simulate a torque motor.
>>
>>
>
>What's R1 (1G to +5) for?

It can be switched in, and R2 switched out, to make an ohmmeter. Then
the opamp is a DC amplifier into an ADC.

>
>Are torque motors actually predominantly inductive? Just
>because it has coils doesn't necessarily mean it is so.

One case is used in some jet engines, for controlling fuel flow I
think. 750 mH and maybe 200 ohms..

Unlike steppers, they seem to have no detent torque and I suspect L
doesn't change much with angular position. Gotta machine a test setup
and verify that.

If the brushes short windings sometimes, it could get weird.

>
>Jeroen Belleman

On 4/9/24 19:17, john larkin wrote:
> On Tue, 9 Apr 2024 17:36:28 +0200, Jeroen Belleman
> <jeroen@nospam.please> wrote:
>
>> On 4/9/24 16:19, John Larkin wrote:
>>> On Mon, 08 Apr 2024 17:17:15 -0700, john larkin <jl@650pot.com> wrote:
>>>
>>>> I can build this into my new programmable inductor module, for
>>>> self-test. With a 1% cap, it should be plenty good. L range will be
>>>> 750 mH down to maybe 10 mH, part of simulating solenoids and torque
>>>> motors and such.
>>>>
>>>> If I add a switch to open R3 and run some current through R1, it can
>>>> measure series resistance too.
>>>>
>>>> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>>>>
>>>> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0
>>>
>>> Most L-meters, the AADE sort, lie or don't work with big Ls.
>>>
>>> This is better:
>>>
>>> https://www.dropbox.com/scl/fi/9tex1slpnaqz4n2cbxp3n/Ind_Meter_Apr_9.jpg?rlkey=52vbyylc5ax48w54qdxm9r9cq&raw=1
>>>
>>> Given a small uP, like the Rasp Pi thing, it could measure L and Rl
>>> pretty easily. One could get compusive and math out the small
>>> inductance measuring error from the inductor copper resistance.
>>>
>>> I need repeatability more than accuracy, and don't have time to
>>> explore this very deep, but it's interesting.
>>>
>>> I've been buying shaftless torque motors off ebay, to understand them
>>> electrically. We need to simulate a torque motor.
>>>
>>>
>>
>> What's R1 (1G to +5) for?
>
> It can be switched in, and R2 switched out, to make an ohmmeter. Then
> the opamp is a DC amplifier into an ADC.
>
>>
>> Are torque motors actually predominantly inductive? Just
>> because it has coils doesn't necessarily mean it is so.
>
> One case is used in some jet engines, for controlling fuel flow I
> think. 750 mH and maybe 200 ohms..
>
> Unlike steppers, they seem to have no detent torque and I suspect L
> doesn't change much with angular position. Gotta machine a test setup
> and verify that.
>
> If the brushes short windings sometimes, it could get weird.

At first sight, if they're like brushed DC motors, the equivalent
circuit would be a series combination of an inductor, a resistor
and a voltage source, function of rotational speed. There will be
some torque ripple and commutator noise, but there's no telling
how important that may be.

Jeroen Belleman

On Tue, 9 Apr 2024 21:13:30 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

>On 4/9/24 19:17, john larkin wrote:
>> On Tue, 9 Apr 2024 17:36:28 +0200, Jeroen Belleman
>> <jeroen@nospam.please> wrote:
>>
>>> On 4/9/24 16:19, John Larkin wrote:
>>>> On Mon, 08 Apr 2024 17:17:15 -0700, john larkin <jl@650pot.com> wrote:
>>>>
>>>>> I can build this into my new programmable inductor module, for
>>>>> self-test. With a 1% cap, it should be plenty good. L range will be
>>>>> 750 mH down to maybe 10 mH, part of simulating solenoids and torque
>>>>> motors and such.
>>>>>
>>>>> If I add a switch to open R3 and run some current through R1, it can
>>>>> measure series resistance too.
>>>>>
>>>>> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>>>>>
>>>>> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0
>>>>
>>>> Most L-meters, the AADE sort, lie or don't work with big Ls.
>>>>
>>>> This is better:
>>>>
>>>> https://www.dropbox.com/scl/fi/9tex1slpnaqz4n2cbxp3n/Ind_Meter_Apr_9.jpg?rlkey=52vbyylc5ax48w54qdxm9r9cq&raw=1
>>>>
>>>> Given a small uP, like the Rasp Pi thing, it could measure L and Rl
>>>> pretty easily. One could get compusive and math out the small
>>>> inductance measuring error from the inductor copper resistance.
>>>>
>>>> I need repeatability more than accuracy, and don't have time to
>>>> explore this very deep, but it's interesting.
>>>>
>>>> I've been buying shaftless torque motors off ebay, to understand them
>>>> electrically. We need to simulate a torque motor.
>>>>
>>>>
>>>
>>> What's R1 (1G to +5) for?
>>
>> It can be switched in, and R2 switched out, to make an ohmmeter. Then
>> the opamp is a DC amplifier into an ADC.
>>
>>>
>>> Are torque motors actually predominantly inductive? Just
>>> because it has coils doesn't necessarily mean it is so.
>>
>> One case is used in some jet engines, for controlling fuel flow I
>> think. 750 mH and maybe 200 ohms..
>>
>> Unlike steppers, they seem to have no detent torque and I suspect L
>> doesn't change much with angular position. Gotta machine a test setup
>> and verify that.
>>
>> If the brushes short windings sometimes, it could get weird.
>
>At first sight, if they're like brushed DC motors, the equivalent
>circuit would be a series combination of an inductor, a resistor
>and a voltage source, function of rotational speed. There will be
>some torque ripple and commutator noise, but there's no telling
>how important that may be.
>
>Jeroen Belleman

They behave about like 2-phase stepper motors. DC applied to the two
windings sets an angular position, not a speed.

On 4/9/24 02:17, john larkin wrote:
> I can build this into my new programmable inductor module, for
> self-test. With a 1% cap, it should be plenty good. L range will be
> 750 mH down to maybe 10 mH, part of simulating solenoids and torque
> motors and such.
>
> If I add a switch to open R3 and run some current through R1, it can
> measure series resistance too.
>
> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>
> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0
>

https://github.com/coreWeaver/LC-Meter/blob/main/LC%20Meter%20v1.0/1.%20Schematic%20and%20Gerber%20UPDATED%20Apr.08%2C%202021/LC%20Meter%20-%20Schematic.pdf

On 09-04-2024 19:17, john larkin wrote:
> On Tue, 9 Apr 2024 17:36:28 +0200, Jeroen Belleman
> <jeroen@nospam.please> wrote:
>
>> On 4/9/24 16:19, John Larkin wrote:
>>> On Mon, 08 Apr 2024 17:17:15 -0700, john larkin <jl@650pot.com> wrote:
>>>
>>>> I can build this into my new programmable inductor module, for
>>>> self-test. With a 1% cap, it should be plenty good. L range will be
>>>> 750 mH down to maybe 10 mH, part of simulating solenoids and torque
>>>> motors and such.
>>>>
>>>> If I add a switch to open R3 and run some current through R1, it can
>>>> measure series resistance too.
>>>>
>>>> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>>>>
>>>> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0
>>>
>>> Most L-meters, the AADE sort, lie or don't work with big Ls.
>>>
>>> This is better:
>>>
>>> https://www.dropbox.com/scl/fi/9tex1slpnaqz4n2cbxp3n/Ind_Meter_Apr_9.jpg?rlkey=52vbyylc5ax48w54qdxm9r9cq&raw=1
>>>
>>> Given a small uP, like the Rasp Pi thing, it could measure L and Rl
>>> pretty easily. One could get compusive and math out the small
>>> inductance measuring error from the inductor copper resistance.
>>>
>>> I need repeatability more than accuracy, and don't have time to
>>> explore this very deep, but it's interesting.
>>>
>>> I've been buying shaftless torque motors off ebay, to understand them
>>> electrically. We need to simulate a torque motor.
>>>
>>>
>>
>> What's R1 (1G to +5) for?
>
> It can be switched in, and R2 switched out, to make an ohmmeter. Then
> the opamp is a DC amplifier into an ADC.
>
>>
>> Are torque motors actually predominantly inductive? Just
>> because it has coils doesn't necessarily mean it is so.
>
> One case is used in some jet engines, for controlling fuel flow I
> think. 750 mH and maybe 200 ohms..
>
> Unlike steppers, they seem to have no detent torque and I suspect L
> doesn't change much with angular position. Gotta machine a test setup
> and verify that.
>

I did some tests on that maybe 10 years back. I can't remember the
details, but I am pretty sure there is a significant change in the
inductance vs position

On Tue, 9 Apr 2024 22:58:30 +0200, Lasse Langwadt <llc@fonz.dk> wrote:

>On 4/9/24 02:17, john larkin wrote:
>> I can build this into my new programmable inductor module, for
>> self-test. With a 1% cap, it should be plenty good. L range will be
>> 750 mH down to maybe 10 mH, part of simulating solenoids and torque
>> motors and such.
>>
>> If I add a switch to open R3 and run some current through R1, it can
>> measure series resistance too.
>>
>> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>>
>> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0
>>
>
>https://github.com/coreWeaver/LC-Meter/blob/main/LC%20Meter%20v1.0/1.%20Schematic%20and%20Gerber%20UPDATED%20Apr.08%2C%202021/LC%20Meter%20-%20Schematic.pdf

Are there specs on that one? I didn't see anything like a manual.

john larkin <jl@650pot.com> wrote:
> On Tue, 9 Apr 2024 17:36:28 +0200, Jeroen Belleman
> <jeroen@nospam.please> wrote:
>
>> On 4/9/24 16:19, John Larkin wrote:
>>> On Mon, 08 Apr 2024 17:17:15 -0700, john larkin <jl@650pot.com> wrote:
>>>
>>>> I can build this into my new programmable inductor module, for
>>>> self-test. With a 1% cap, it should be plenty good. L range will be
>>>> 750 mH down to maybe 10 mH, part of simulating solenoids and torque
>>>> motors and such.
>>>>
>>>> If I add a switch to open R3 and run some current through R1, it can
>>>> measure series resistance too.
>>>>
>>>> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>>>>
>>>> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0
>>>
>>> Most L-meters, the AADE sort, lie or don't work with big Ls.
>>>
>>> This is better:
>>>
>>> https://www.dropbox.com/scl/fi/9tex1slpnaqz4n2cbxp3n/Ind_Meter_Apr_9.jpg?rlkey=52vbyylc5ax48w54qdxm9r9cq&raw=1
>>>
>>> Given a small uP, like the Rasp Pi thing, it could measure L and Rl
>>> pretty easily. One could get compusive and math out the small
>>> inductance measuring error from the inductor copper resistance.
>>>
>>> I need repeatability more than accuracy, and don't have time to
>>> explore this very deep, but it's interesting.
>>>
>>> I've been buying shaftless torque motors off ebay, to understand them
>>> electrically. We need to simulate a torque motor.
>>>
>>>
>>
>> What's R1 (1G to +5) for?
>
> It can be switched in, and R2 switched out, to make an ohmmeter. Then
> the opamp is a DC amplifier into an ADC.
>
>>
>> Are torque motors actually predominantly inductive? Just
>> because it has coils doesn't necessarily mean it is so.
>
> One case is used in some jet engines, for controlling fuel flow I
> think. 750 mH and maybe 200 ohms..
>
> Unlike steppers, they seem to have no detent torque and I suspect L
> doesn't change much with angular position. Gotta machine a test setup
> and verify that.
>
> If the brushes short windings sometimes, it could get weird.
>
>
>
>>
>> Jeroen Belleman
>

They won’t have nice linear ferrite cores but nasty lumps of iron so
measured inductance could depend on test frequency, AC amplitude, amount of
DC flowing, rotor position, temperature etc etc etc. Precision is futile?

--
piglet

On 10/04/2024 4:29 pm, piglet wrote:
> john larkin <jl@650pot.com> wrote:
>> On Tue, 9 Apr 2024 17:36:28 +0200, Jeroen Belleman
>> <jeroen@nospam.please> wrote:
>>
>>> On 4/9/24 16:19, John Larkin wrote:
>>>> On Mon, 08 Apr 2024 17:17:15 -0700, john larkin <jl@650pot.com> wrote:
>>>>
>>>>> I can build this into my new programmable inductor module, for
>>>>> self-test. With a 1% cap, it should be plenty good. L range will be
>>>>> 750 mH down to maybe 10 mH, part of simulating solenoids and torque
>>>>> motors and such.
>>>>>
>>>>> If I add a switch to open R3 and run some current through R1, it can
>>>>> measure series resistance too.
>>>>>
>>>>> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>>>>>
>>>>> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0
>>>>
>>>> Most L-meters, the AADE sort, lie or don't work with big Ls.
>>>>
>>>> This is better:
>>>>
>>>> https://www.dropbox.com/scl/fi/9tex1slpnaqz4n2cbxp3n/Ind_Meter_Apr_9.jpg?rlkey=52vbyylc5ax48w54qdxm9r9cq&raw=1
>>>>
>>>> Given a small uP, like the Rasp Pi thing, it could measure L and Rl
>>>> pretty easily. One could get compusive and math out the small
>>>> inductance measuring error from the inductor copper resistance.
>>>>
>>>> I need repeatability more than accuracy, and don't have time to
>>>> explore this very deep, but it's interesting.
>>>>
>>>> I've been buying shaftless torque motors off ebay, to understand them
>>>> electrically. We need to simulate a torque motor.
>>>>
>>>>
>>>
>>> What's R1 (1G to +5) for?
>>
>> It can be switched in, and R2 switched out, to make an ohmmeter. Then
>> the opamp is a DC amplifier into an ADC.
>>
>>>
>>> Are torque motors actually predominantly inductive? Just
>>> because it has coils doesn't necessarily mean it is so.
>>
>> One case is used in some jet engines, for controlling fuel flow I
>> think. 750 mH and maybe 200 ohms..
>>
>> Unlike steppers, they seem to have no detent torque and I suspect L
>> doesn't change much with angular position. Gotta machine a test setup
>> and verify that.
>>
>> If the brushes short windings sometimes, it could get weird.

Why would you need brushes in a torque motor?

> They won’t have nice linear ferrite cores but nasty lumps of iron so
> measured inductance could depend on test frequency, AC amplitude, amount of
> DC flowing, rotor position, temperature etc etc etc. Precision is futile?

Not futile but probably difficult to achieve. Lots of variables to
measure and correct for, and non-linear correction equations.

--
Bill Sloman, Sydney

On Tue, 9 Apr 2024 21:13:30 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

>On 4/9/24 19:17, john larkin wrote:
>> On Tue, 9 Apr 2024 17:36:28 +0200, Jeroen Belleman
>> <jeroen@nospam.please> wrote:
>>
>>> On 4/9/24 16:19, John Larkin wrote:
>>>> On Mon, 08 Apr 2024 17:17:15 -0700, john larkin <jl@650pot.com> wrote:
>>>>
>>>>> I can build this into my new programmable inductor module, for
>>>>> self-test. With a 1% cap, it should be plenty good. L range will be
>>>>> 750 mH down to maybe 10 mH, part of simulating solenoids and torque
>>>>> motors and such.
>>>>>
>>>>> If I add a switch to open R3 and run some current through R1, it can
>>>>> measure series resistance too.
>>>>>
>>>>> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>>>>>
>>>>> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0
>>>>
>>>> Most L-meters, the AADE sort, lie or don't work with big Ls.
>>>>
>>>> This is better:
>>>>
>>>> https://www.dropbox.com/scl/fi/9tex1slpnaqz4n2cbxp3n/Ind_Meter_Apr_9.jpg?rlkey=52vbyylc5ax48w54qdxm9r9cq&raw=1
>>>>
>>>> Given a small uP, like the Rasp Pi thing, it could measure L and Rl
>>>> pretty easily. One could get compusive and math out the small
>>>> inductance measuring error from the inductor copper resistance.
>>>>
>>>> I need repeatability more than accuracy, and don't have time to
>>>> explore this very deep, but it's interesting.
>>>>
>>>> I've been buying shaftless torque motors off ebay, to understand them
>>>> electrically. We need to simulate a torque motor.
>>>>
>>>>
>>>
>>> What's R1 (1G to +5) for?
>>
>> It can be switched in, and R2 switched out, to make an ohmmeter. Then
>> the opamp is a DC amplifier into an ADC.
>>
>>>
>>> Are torque motors actually predominantly inductive? Just
>>> because it has coils doesn't necessarily mean it is so.
>>
>> One case is used in some jet engines, for controlling fuel flow I
>> think. 750 mH and maybe 200 ohms..
>>
>> Unlike steppers, they seem to have no detent torque and I suspect L
>> doesn't change much with angular position. Gotta machine a test setup
>> and verify that.
>>
>> If the brushes short windings sometimes, it could get weird.
>
>At first sight, if they're like brushed DC motors, the equivalent
>circuit would be a series combination of an inductor, a resistor
>and a voltage source, function of rotational speed. There will be
>some torque ripple and commutator noise, but there's no telling
>how important that may be.
>
>Jeroen Belleman

https://www.dropbox.com/scl/fo/d9qffkwqzikd9visdt0zi/h?rlkey=mdon4i9xblxkerk470umdbsw3&dl=0

This is charmingly bizarre. There are 41 (prime number!) of commutator
segments. If I pick one arbitrarily, and call it #1, and go clockwise
with an ohmmeter, resistance goes up to about 8 ohms in steps and goes
back down to about 1 ohm at commutator 17, 26, and 34.

This is an NOS motor from ebay. It's an older style with brushes and
alnico magnets.

Imagine designing this 50 years ago without a computer.

On 4/10/24 05:18, John Larkin wrote:
> On Tue, 9 Apr 2024 22:58:30 +0200, Lasse Langwadt <llc@fonz.dk> wrote:
>
>> On 4/9/24 02:17, john larkin wrote:
>>> I can build this into my new programmable inductor module, for
>>> self-test. With a 1% cap, it should be plenty good. L range will be
>>> 750 mH down to maybe 10 mH, part of simulating solenoids and torque
>>> motors and such.
>>>
>>> If I add a switch to open R3 and run some current through R1, it can
>>> measure series resistance too.
>>>
>>> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1
>>>
>>> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0
>>>
>>
>> https://github.com/coreWeaver/LC-Meter/blob/main/LC%20Meter%20v1.0/1.%20Schematic%20and%20Gerber%20UPDATED%20Apr.08%2C%202021/LC%20Meter%20-%20Schematic.pdf
>
> Are there specs on that one? I didn't see anything like a manual.
>

afaict there's a video explaining all the fucntions and equations
https://github.com/coreWeaver/LC-Meter