Help intagrating hertzmeter into analog linear power supply

[DyingART]

First off I'm not an engineer nor do I have a electronics background.
I have an old Linear (HP 6284A Power Supply). I would like to be able to display Hz/CPS.

I need to measure the speed of a tattoo machine. (basically two coils that make and break connection through out its use.

From what I gather I need circuitry to measure the waveform of the output current, an analog-to-digital converter to get that waveform data into a microcontroller, a microcontroller to analyze the waveform, software to extract the three time intervals.

Or is there is there a simpler way?
Help?!

What do I need to buy to make this work :)

 

[Borek]

Some universal meters (like this one) measure frequency. About $40 on ebay. Plus many more specialized frequency meters that will be even cheaper. Won't they suffice?

 

[DyingART]

I'm not sure how they work.. The output for the power supply is DC so...?

 

[anorlunda]

There is a much simpler way. Use the sound. There are apps for phones and tablets that display the frequency of a musical note.

 

[DyingART]

Interesting.. Though the Hertz level will be between 0-120. I'm not sure a program designed for musical notes will register that low? I'll try it. I would really like to integrate it into the power supply and build something like this. http://criticaltattoo.com/cx2r-g2/

This isn't for profit BTW.. Its for personal use. I would just buy a power supply for the job but they are expensive and hardly quality power.

 

[Asymptotic]

If you play guitar you might have a tuner handy. The frequency range of my $25 Korg CA-30 tuner is listed as C1 through C8 (32.7 Hz to 4186.1 Hz), but it registers down to about 31.79 Hz (50 cents under C1). My guess is most musical instrument tuners don't go down very much farther than that (the lowest piano key, A₀, is 27.5 Hz).

An HP 6284A supply is rated is 0-20 VDC at 0-3 amps. Is it fair to say that voltage adjustment doesn't affect machine speed?
Do you want to measure speed for machine adjustment?

Another approach is to run the tattoo machine, and adjust the frequency of a tone generator until it's output tone matches the tattoo machine.

 

[DyingART]

Voltage adjustment does affect machine speed. Would be nice to know the speeds.

 

[Asymptotic]

Voltage adjustment does affect machine speed. Would be nice to know the speeds.

Does loading affect speed appreciably? If not,

1. Operate the machine at full voltage. Determine the frequency by matching it's sound to an adjustable tone generator. Record voltage and frequency.
2. Incrementally reduce voltage by a small amount (say, 0.25V). Find the new frequency. Write it down. Continue this until at zero volts (or at whatever low voltage stalls the tattoo machine).

My guess is the relation between applied voltage and tattoo machine frequency is fairly linear and repeatable. Once you've determined voltage versus frequency, adjust the machine to whatever voltage yields the desired speed (frequency).

I need circuitry to measure the waveform of the output current, an analog-to-digital converter to get that waveform data into a microcontroller, a microcontroller to analyze the waveform, software to extract the three time intervals

Doing something like this is an option, although probably not by directly measuring pulsations in output current, but rather by adding a low ohmic value resistor, and measuring voltage drop across it.

If there is a dramatic difference between high and low current demand per cycle it should be possible to isolate and count the high current pulses, and scale them to display in CPS. The less dramatic the difference in maximum and minimum current demand, the harder it is to tell them apart, and more difficult it is to determine machine speed through current feedback.
.

 

[DyingART]

GENERALLY ACCEPTED HERTZ/CPS Readings:
Liner 130 to 145
Shader 105 to 120
Color Packer, 95 to 115

The problem with recording voltage vs frequency incrementally Is the load on the springs/coils of the machine will be different with different needle groupings (weight).

 

[Asymptotic]

GENERALLY ACCEPTED HERTZ/CPS Readings:
Liner 130 to 145
Shader 105 to 120
Color Packer, 95 to 115

The problem with recording voltage vs frequency incrementally Is the load on the springs/coils of the machine will be different with different needle groupings (weight).

Those speed ranges are well within musical instrument tuner capabilities. Here is a KLIQ Metropitch as an example. I can't tell if it displays in Hz as well as in musical pitch (on my Korg, the Hz value is calibration above and below 440 Hz, not note frequency).

It may seems strange at first, but if the idea is to repeatably tune the tattoo machine to a particular speed then use a chromatic tuner, and think about the speeds in terms of musical notes (130 Hz to 145 Hz is just about C₃ to D₃)

 

[Tom.G]

If an analog output (a moving needle like on the speedometer of a car) meets your needs and you want to build-it-yourself, try this search:
https://www.google.com/search?source=hp&q=555+frequency+meter&oq=555+frequency+meter

Otherwise, as stated above by many, a prebuilt one for musical use is your best bet.