Hi all, I'm new to the forum and new to electronics.

I do, however, mess around in Hifi and build, refurb and play with record players.

I have a project in mind to build a speed controller for the standard speeds of a turntable and have a design project for this however to give it an old school look I want to incorporate a set of Nixie tubes to display the speeds produced by the controller.

I'm not really sure what I need to produce this and as I said have no knowledge of the subject but am eager to learn.

So a wide reaching question for you guys and any help would be greatly appreciated.

 

How many digits?

 

I'm thinking four 33.33 45.00 and 78.00 are the standard speeds the controller would aim for and be adjustable to.

 

A micro-controller could measure the speed and display it nicely.
Nixie tubes just need some high-voltage NPN transistors to drive them, not too complex.
Use a few shift register / latches to interface the micro to the transistors.

It's much harder to do this with hardware alone.

 

Thanks for the replies, As I mentioned this is all new to me and whilst I'm happy to research what you are telling me, and I am getting the gist of it, I have to confess I am a complete novice and wasn't given the electronics 'babel fish' I'm already way outta my depth and its only been a couple of posts. Please don't get me wrong I'm keen to find out but I guess I'm better off starting at the bottom.

I'm over in the UK so maybe my question should be is there anyone over here that could put something together for me to do the job, refer me to a kit of some kind or explain in baby language what to do.

 

OK I've progressed a little and have my eye on a ready made Nixie clock with 6 digits and two decimal points. Run through the Arduino system and programmed using C++. The chip will be pre-installed with the clock programming however I'm wondering if I could introduce somewhere into the program an additional section to display the tacho program. I'm thinking of using a hall effect sensor and magnet on the platter of the turntable fed through to the board and chip. The readings from there displayed on the nixies.

Anyone played around with the Arduino system and had multi programs running?

 

It's been a little while since I started this and although a few comments were given it wasn't a great deal of help so I muddled along. I tend to do that

Anyway for those of you who may have been a little interested in my project here's where I am.

I bought one of these, a nixie clock with Arduino board and program.

I then bought me some electronics stuff

and turned it all into this

Eventually it'll be keeping the control of the speed on this little project.

Now for all you young things, and I know this forum will be mainly inhabited by the young brains of the world, This is old school. This is a Lenco L75 turntable, cut into a pizza pan with a multi layered plinth of a quite unique style. It still has a little way to go, as has the Speed Controller, but I'd like to get them done so that I may reap the sweet rewards of an LP playing at perfect speed with that little orange glow of the nixies letting me know that the correct speed is turning the vinyl and the notes I hear are spot on.

So How do I add to the programming of the clock an extra function in the current button press to allow me to select the tachometer mode and run the tacho program for the hall effect sensor that will be added to the platter?

Anyone fancy a real challenge in helping an old fogey out with this project?

Psst there might be a reward in it for somebody

 

Sensor output
Buffer, gain, frequency filtering, whatever
Digital processing functions
Output to display subsystem

The nice thing about having a microcontroller in the project is that there does not have to be a direct, or even a harmonic relationship between the sensor frequency and the platter speed. But usually there is anyway, so what is it? At 33 RPM, what is the frequency of the Hall sensor signal?

A digital clock is an incremental counter, designed to count at a 1 Hz rate and roll over occasionally but never reset to zero and start over. Hopefully the Hall sensor signal is many times that frequency, and is to be counted up and then displayed frozen while the next count-up happens. Do you have a plan for adapting the clock assembly to this very different signal, or is that what you are asking for help with?

Nice woodworking.

ak

 

Sensor output
Buffer, gain, frequency filtering, whatever
Digital processing functions
Output to display subsystem

The nice thing about having a microcontroller in the project is that there does not have to be a direct, or even a harmonic relationship between the sensor frequency and the platter speed. But usually there is anyway, so what is it? At 33 RPM, what is the frequency of the Hall sensor signal?

A digital clock is an incremental counter, designed to count at a 1 Hz rate and roll over occasionally but never reset to zero and start over. Hopefully the Hall sensor signal is many times that frequency, and is to be counted up and then displayed frozen while the next count-up happens. Do you have a plan for adapting the clock assembly to this very different signal, or is that what you are asking for help with?

Nice woodworking.

ak

Thanks for the response AK the hall sensor is purely to count the revs of the turntable. The adjustment of the revs is dealt with independently by the speed controller which is adjusted by pots within its circuitry. It's the programming of the clock program to allow a further function that would then allow the tacho program to independently display on the nice tubes. I could have a second Arduino board running the tacho program but how then do I get two boards to display to the set of tubes. To clarify the clock and the tacho will not be running at the same time, the switch function would allow you to choose. Currently you can display the time or date or the clock setting function or date setting function. I want to add another to change it to the tacho function.

If you get what I mean

 

It sounds like the clock has its own microcontroller and you want to reprogram it. Do you have the original source code? Alternatively, the clock has a dedicated clock chip which is not programmable. Is information about the clock a secret?

ak

 

Without access to the clock's source code I don't see how it is possible to just add some extra code to add the functions you want.

If you want a functioning clock and a turntable speed read-out you will need to start from the beginning and write the code for both since they will be interlinked to some extent.

 

What you need is some 74141 ICs to drive the nixie tubes. This IC is not made any more but it is still possible to get them. There are also some Russian copies on the market (not all of them work!). These convert BCD (4-wires) to 10 high-voltage outputs to drive the cathodes in the nixie tubes.You will also need a 120V power supply to power the tubes.

Then, I would build a micro-controller circuit to do the speed measuring and drive the 74141s.

Some time ago I acquired a PCB that had 6 nixie tubes and 6 74141 ICs on it. So I used a PIC16F871 micro-controller to make a digital clock. This micro-controller has 40 pins so plenty of I/O to get all the BCD outputs without any multiplexing. I would be fairly simple to write some code that takes a signal from a sensor and computes the RPM.

 

Hi Guys and thanks for the replies. I have the clock and the code for the same. I have no experience in coding although I believe it is in some form of C+ I can see in the code there are separate sections for the selection of the different modes and my thinking is that a further selection choice is added, taking the display to the tacho mode then using code for the Arduino tacho outputting its display to the board. This is already setup and working as the clock so the drivers etc are all in place and programmed to the Arduino clock coding.

The clock details are on Github https://github.com/afch/NixieClock

I have found a suitable Tacho program for the hall effect sensor though its output is to a standard led display, so just need to combine the two and change the display output in the code for the HES to use the nixies. Can I use the clock Arduino board to run the sensor aswell or would it be better to have this on a second board and if so how would I go about outputting this to the first board to use the nixies?

I hope this makes sense to you guys

 

What is the Hall sensor sensing? Are there magnets glued to the underside of the turntable platter, or what?

ak

 

What is the Hall sensor sensing? Are there magnets glued to the underside of the turntable platter, or what?

ak

Yup exactly that, each revolution will be detected.

 

Why is this so hard... How Many Magnets? How Many Pulses Per Platter Revolution? (Hint: odd number = bad)

At 33 RPM, what is the frequency of the Hall sensor signal?

ak

 

Why is this so hard... How Many Magnets? How Many Pulses Per Platter Revolution? (Hint: odd number = bad)


ak

OK the number of magnets can be as many as required though ideally I'm guessing one,two or four would be best. (more and you have to start relying on perfect placement to avoid misreadings. Therefore the programming of the reporting will need to take in calculations based on the above. The tacho program code deals with this based on one magnet although at only 33.3 revs per min it's questionable if it will be enough to update sufficiently to give an accurate reading.

This bit I'm not too worried about at the moment it's if I can get the programming for the tacho to run with the clock code and the hall sensor to run along side the clock on the one Arduino board.

Please bear in mind I am a complete novice with this stuff, never programmed had little experience with electronics and prefer records to MP3's

 

One magnet giving one pulse per revolution will be fine. If more than one then it will be difficult to accurately place at the exact number of degrees and the display will flicker about.

You need a crystal-controlled oscillator (could be the micro-controller clock) . Count the number of clock pulses between sensor pulses. The display will update each revolution. Even at 331/3 rpm update rate should be sufficient.

 

Hi Marley, Surely the HES will be dealing with this?

OK, and this is as much for my benefit as well as setting out where I am, what I've got so far is as follows:

One turntable which will have connected to the platter a/some magnets (very tiny and will not affect the cartridge above).

One Hall Effect Sensor (HES) which will be fixed under the platter on top of the base plate to detect the magnet on each revolution of the platter. The reading from the HES will, via the coding on the Arduino board, output the RPM (currently programmed to an LED). The output will be to the nixie tubes.

One speed controller for the motor of the turntable which can by way of potentiometers increase or decrease the power of the motor thereby speeding up or slowing down the platter to the correct speed.

One six nixie tube clock based on an Arduino circuit outputting to nixie tubes.

What I need help with is:

Can the Arduino board for the clock take a second program and hardware for the HES Tacho?

Can both programs (and associated hardware) output to the same Nixie tubes?

Can the clock code run, as a separate component of the coding, the tacho code?

Hmmm is this all worth it? HECK YES!" When I get it running it'll be cool

 

In terms of audio quality, one magnet is the worst possible arrangement because it is an unbalanced load on the bearings.

Separate from that, you don't want an instantaneous display of revolution-by-revolution speed. A small bit of traveling averaging in the uC code will make minor errors in magnet placement disappear while giving a *more* accurate result. This is the technique used by the US Naval Observatory to determine the national time of day - they average 50 atomic clocks.

Also, at such low frequencies, many frequency counters in fact measure the period between pulses and invert the number to get the frequency. This is what post #18 is referring to.

ak