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JOHNNYCR100 2nd January 2017 01:39 PM

Digital Tachometer for record player (LCD display)
Avast Gents, happy new year.

I have been contemplating a tachometer for my record player with a digital readout LED or LCD--(making one as opposed to buying one as we know they already exist a la roadrunner... but are to expensive for my meager budget:eek:)

There are lots of examples on the new of using ardunio and a hall effect sensor but these are for drill and lath speeds, not 33.33RPM as we would require.
Numerous cheap (and nasty?) -- Car tachometer modules abound on e bay -but are they accurate enough for record player use??.
Some interesting propitiatory modules were about but when contacted the makers do not produce these items any more!

What would be great is an ardunio based (accurate) Tachometer with a hall effect sensor, and the possible option of using a touch screen to turn the record player motor on/off which could via the arduneo switch a relay on/off---(think project had this in one of there high end turntables?)

I have the brains to buy the items, but to code this...nah i be flabbergasted!:D

Is anyone of you good gents (or ladies..i aint proud) shed any light on such a project.... i am aware that that git hub can download library's for buttons on a LCD..and code exits for tachometer functions (counts time between magnet pulses and works out RPM from that?)...but how to integrate it all from a newsboys point of view??
Fingers crossed then.

cheers ..johnny

jrubins 2nd January 2017 06:35 PM

It should be reasonably easy to do via hall effect sensor or optical encoder
Here's on using hall effect and an arduino Asciimation Blog Archives More on the steampunk-o-phone.

JOHNNYCR100 3rd January 2017 02:10 PM

Thanks for the reply sir
Hi Jrubins,
Thank you.

Interesting link, shows the Arduino is quite good for this sort of thing, the speed indication via an analogue meter is something i have considered, but i would have a dynamic (digital numerals) indication- guess you would have to set it up by ear first, then make off the correct point on the meter that is 33.33 RPM (hopefully!)

As my design is not so steampunk, I won’t go that way, but it shows the Arduino is well up to this as it has PWM and A/D converters on board (unlike the Rasp Pi)
A project signature type of controller is what i was thinking of trying to emulate, I know this can be achieved with an Arduino (somehow!)…any takers boys (or girls) see this link:
[Review] Pro-Ject Signature 12 Turntable


Pyramid 3rd January 2017 05:19 PM

Thanks for the link to the Pro-Ject S12. It doesn't appear that the table actually measures or displays the platter speed (still used a strobe disc to set speed). The display is similar to the MH Cruise Control ($299) or the VPI SDS ($1400).

You can build your own version of a digital PSU (in fact better than either of those) for ~$100:

jrubins 3rd January 2017 06:33 PM

Clearaudio uses an optical encoder to measure speed, feeding back to the controller. Many motors have similar features built in, which pyramid's controller can make use of to keep the speed rock-solid.
If all you want is a tachometer though, you can build an optical one with a standard strobe disk and something like this

Sent from my iPhone using Tapatalk

JOHNNYCR100 4th January 2017 08:51 PM

Thank you both for the replys
:mad:Hi Pyramid and Jrubins,

Well..if i was aware of the initial project by pyramids i may have gone for that, but i have built a Mark Kelly speed controller and got a maxton motor, and had a pad made for it, so i have to go that way, I was aware of the info on the ardunio based taco project, and may buy the bits needed and have a go.. (but how accurate are they, they all seem to be measuring high RPM from drills and laths (not 33.33 RPM low record platter speeds?)
Some vendors sell integrated ardunio and display packages but they only seem to measure voltages and temperature, do they have access to the boot loader to re program?..if so how do you know the scrip you down load will support the display that the vendor has already soldered to the ardunio??..this kind of thing puzzles me:mad:

JOHNNYCR100 4th January 2017 08:54 PM

Alternatively hack one of these items?::confused:

Digital Laser Photo Tachometer Non Contact RPM Tach Tester RPM Motors | eBay

Not to expensive is it?


tauro0221 4th January 2017 09:43 PM

5 Attachment(s)
I built one controller to control the speed of a Garrard 35 turntable and it worked very good until I tried to paint it. It end the trash can. I used an optical infrared optical sensor to read the index reflection from a strip glued to the inside rim of the plate. I tried the hall effect but the magnetic field radiated from the stepper motor had some conflicted with the pulses. The way it works it is to read the time it takes one revolution and calculate the rpm then display it in the lcd display. The sound was very good and it keep the rpm on target. I used the stepper motor because they are cheap and easy to control using the pwm control. The only problem it is that I used the Zbasic micro and their software for the programming. It is an easy project to do using the optical sensor. Attached rea some pictures showing how I built it.

JOHNNYCR100 4th January 2017 10:36 PM

Hi Tauro0221,

Thanks for the reply, did you use an Ardunio or something else, and did you originate the code yourself or was it from the internet or whatever?
Sorry for all the questions, but it seem a nice accurate project and i already have a motor controller to spin the platter.


tauro0221 5th January 2017 01:57 AM

I used the Zbasic micro. They use the 328 same as Arduino but with a different bootloader. I think if you do not use the speed control you can modify the program for Arduino. I used the Photologig reflective object sensor part number OPB761 from Mouser to read the index pulse and then calculate the rpm by the time it is taking to completed one complete revolution. It is a TTL output sensor. I developed the software. It is a simple equation.

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