I am an audiophile and a tinkerer. I am an old hand at mechanical fabrication & electronics, but have no background or experience using an arduino board. Let me first lay out the design parameters:
The object of this project is to develop and fabricate a simple cheap and functional end of record tonearm lift for manual turntables. This could be done by actuating the existing manual tone arm lift mechanism, but it would be preferable to have a separate lift device that functions independent of the existing manual lift
Here are the basic functions a servo or gear reduction motor would have to do and what signals it would have to respond to:
The servo would need to have an arm mounted to its shaft that when rotated would lift the tone arm. A very small angle of rotation is required if it is independent of the manual tonearm lift. If it engages the manual tone arm lift it will need to rotate a greater distance. The distance is dependent on the make & model of turntable/ Tonearm.
The default mode of the motor is in the down position
When the tone arm reaches the end of the record a proximity sensor or proxy switch will signal the motor to raise.
The motor must remain in the high position as long as the tonearm remains at the end of the record.
Upon returning the tonearm to the beginning of the record the motor must return to the down position and remain there until the tonearm reaches the end of the record again and the process is repeated.
Perhaps someone has already done this. I would be interested to hear about your experiences.
At first I was going to do this with a small 3 volt gear reduction motor and control it with relays. However when researching the topic I kept coming up with Arduino motor and servo controllers. So here I am!
I presume the existing lift is a horizontal arc which keeps the arm at a constant height across its travel from the inside to the outside of the record. Will the servo arm do the same?
I do not expect someone to design this for me. I just would like to know what I need to have on hand before I start in.
Here are some more questions:
Can this all be done with an Arduino uno r3?
What other hardware will be required?
What would be best, A miniature gear reduction motor or a miniature servo motor?
I assume I will also need a power supply to power the Arduino and motor. There will be no computer attached to the Arduino once it is finished.
Will any shields be required?
I would like to stay away from inductive sensors. I'm concerned about electromagnetic interference. What would be better optical visible light? infrared?
The turntable is a Thorens TD-124 with a SME 3009 tonearm.
For sensing the arm location: break beam sensor, using IR.
For the motion of the arm: easiest would be a servo as it has absolute positioning. Many micro servos can do only
about 120 degrees of motion, the better ones 180 degrees. That should be enough to push back the arm.
But aren't there three movements total involved? First lift the arm off the record, then move it back to its support stand (or however you call that), and then lowering it again. That can not be done with a single servo. It would require some kind of linear actuator to lift/lower the arm.
There is only one movement to lift. I can return the tonearm to its rest manually. This is no hardship because I would be getting up anyway to flip the LP. The only purpose of the auto lift is if I get distracted it will prevent the stylus from getting worn out spinning forever at the end of the LP. It is just a nice addition if the auto lift arm would raise and hold until I can attend to the tone arm then automatically lower so the tone arm does not run into it upon the next play. I have used an Audio Technics AT-6006 Safety Raiser, But sometimes I forget to reset it before playing the second side of the LP. This is due to the occasional senior moment I am subject to.
You have a sensor that detects the arm is at the end position, which will raise it. Mount this sensor in such a way that it remains triggered as the arm is pushed up. If you use a light beam set it at a bit of an angle so the upward motion pushes the arm more in the beam, making sure it's detected. Then when you (manually) move the arm to the rest position and out of the sensor beam then (possibly after some delay) it can lower the raiser.
dougp:
I presume the existing lift is a horizontal arc which keeps the arm at a constant height across its travel from the inside to the outside of the record. Will the servo arm do the same?
It doesn't have to. It only needs to lift the arm at the end of the record. However, where the lift will sit, there isn't much tonearm movement that close to the pivot point so the lift would pick up the arm for most of the record should it trigger early.
That makes me think of another mod. How about having a remote control pause option.
Just thought of this. What I think you're describing is the servo rotating its horn to lift the tonearm. The native lift raises the tonearm vertically. Will yours? Is it important?
I wouldn't use a servo. A servo is an angular motor that rotates less than 360 degrees. It could be made to work, but it might not be smooth. I'd use a geared-down DC motor.
With an H-driver, a DC motor can be reversed or stopped. Or, the same can be accomplished with two relays (one to reverse and one to run/stop).
For the input-logic you'd need 3 sensors - An end-of record sensor and two limit-sensors for the up/down movement. (You'd also want mechanical stops.)
For the output, there are 3 states - Move-up, move-down, and stop.
..If you were doing this "in production" you wouldn't use a programmable microcontroller. The logic is simple enough that it could be done with and/or logic gates. But for a hobbyist, it depends on if you're better at electronics or programming.
Bit late here - but what do you do now to raise the stylus? Is it some sort of lever? If so why not use the existing lever and maybe a cord or something to raise the stylus? eliminates building a lifter device and keeping the device out of the way of the record - then when you have rotated the arm back to the proper position have a button you push that lowers the arm - that "only" leaves you with the arm position sensor and uses the existing lift mechanism
dougp:
Just thought of this. What I think you're describing is the servo rotating its horn to lift the tonearm. The native lift raises the tonearm vertically. Will yours? Is it important?
My plan was to use and "L" shaped arm on the axis of the motor/servo. then turn the motor/servo 90 degrees from the position shown in your diagram. Then the lifting leg of the "L" would lift vertically. It would slide lengthwise along the under side of the tonearm.
dougp:
Just thought of this. What I think you're describing is the servo rotating its horn to lift the tonearm. The native lift raises the tonearm vertically. Will yours? Is it important?
My plan was to use and "L" shaped arm on the axis of the motor/servo. then turn the motor/servo 90 degrees from the position shown in your diagram. Then the lifting leg of the "L" would lift vertically. It would slide lengthwise along the under side of the tonearm.
DVDdoug:
I wouldn't use a servo. A servo is an angular motor that rotates less than 360 degrees. It could be made to work, but it might not be smooth. I'd use a geared-down DC motor.
With an H-driver, a DC motor can be reversed or stopped. Or, the same can be accomplished with two relays (one to reverse and one to run/stop).
For the input-logic you'd need 3 sensors - An end-of record sensor and two limit-sensors for the up/down movement. (You'd also want mechanical stops.)
For the output, there are 3 states - Move-up, move-down, and stop.
..If you were doing this "in production" you wouldn't use a programmable microcontroller. The logic is simple enough that it could be done with and/or logic gates. But for a hobbyist, it depends on if you're better at electronics or programming.
Thanks for this advice. I am better at electronics at this point. I used to be good at programing, but haven't done any in decades. To give you and idea of how old I am, I learned Fortran on Key Punch Cards. I used to be a wiz at fortran. I have also worked in a machine shop and learned machine "G" code. I don't suppose with CAD-CAM there is much value in knowing how to use "G" code anymore either.
Also, I like the gear motor plan.
One of the objects of this project is to learn about the Arduino board. I may be an old dog, but I love to learn new tricks
Slumpert:
And here I come along with the crazy simple..
The goal is to not have the stylus endlessly loop.
Setup a AC power switch controlled by the arduino that turns off the turntable after predetermined time periods or monitor the arm to interrupt power.
Unwanted wear and tear on the stylus, motor, belt is now avoided.
I don't think this will work for my turntable. It is a transcription table that is designed to be running 24-7. The platter never stops turning. There is a secondary platter that rides on the primary (always spinning) platter. To stop to change records one slides a lever on the side of the platter. This moves a mechanical arm that lifts the secondary platter off the primary platter. For a better description I bet there is a Youtube video that shows how the Thorens TD-124 works.
saildude:
Bit late here - but what do you do now to raise the stylus? Is it some sort of lever? If so why not use the existing lever and maybe a cord or something to raise the stylus? eliminates building a lifter device and keeping the device out of the way of the record - then when you have rotated the arm back to the proper position have a button you push that lowers the arm - that "only" leaves you with the arm position sensor and uses the existing lift mechanism
I have been considering this as one of the options. There isn't much room on the right hand side of the table under the dust cover. The original tonearm lift lever almost comes in contact with the dust cover when the cover is down and the tonearm is raised. That being said. It would be a good option. Then the motions of the gear motor/servo is Lift and remedially return to the rest position. The original left lever is designed to stay in the up position. When the record is flipped you would push the lever back down again.
Jagman:
There is a secondary platter that rides on the primary (always spinning) platter. To stop to change records one slides a lever on the side of the platter. This moves a mechanical arm that lifts the secondary platter off the primary platter. For a better description I bet there is a Youtube video that shows how the Thorens TD-124 works.
Would it work to operate that lever instead? It'd lift the arm with the record and all. Could be simpler (less modifications).
