Who is interested in a groupbuy of Mark Kelly's DC controller PCB and related parts

[arnoldc]

Hi Mark, thanks for the reply. I hope you don't mind another one-

- What kind of pulley will be supplied?
- That pulley will dictate the kind of belt, right? So what kind of belt will I need?
- Do you have friends there in Oz who own a Clearaudio and used the kits?

Thanks again for you patience. I am contemplating on a motor, board with standard parts, and pulley.

[Matt Rowland]

Hi Mark,

Thanks for the info’. I’ve already bought the motor, it was expensive, so I’ll have to make the best of it. I calculate that with an 8mm dia pulley and the linn sub-platter dia of 160mm that gives a ratio of 20:1. So 33.33rpm x 20 = about 667 rpm. Given a speed constant of 185rpm/v this implies a drive voltage of about 3.6volts.
So if my motor is running at over 600rpm will the speed variation drop to below 0.1%? Also you say “0.1% per ohm of effective impedance”, what is the effective impedance in this case?

Thanks again

regards


Matt

[Mark Kelly]

Originally posted by arnoldc
- What kind of pulley will be supplied?
- That pulley will dictate the kind of belt, right? So what kind of belt will I need?
- Do you have friends there in Oz who own a Clearaudio and used the kits?

We haven't yet decided on what to do as the "standard" pulley - I was going to ask Vinyl Addict to look at this. I would encourage the use of a tape belt as they will give better performance than a rubber belt.

No I don't know anyone with a Clearaudio.

Originally posted by Matt Rowland
So if my motor is running at over 600rpm will the speed variation drop to below 0.1%? Also you say “0.1% per ohm of effective impedance”, what is the effective impedance in this case?

The higher speed reduces the variability from the motor but the smaller diameter of the subplatter increases it, you should get better than 0.04% with that combination. The effective impedance is the sum of the winding resistance of the motor (about 9 ohms for your motor) and the output impedance of the supply which is variable to suit, you should be able to achieve better than one ohm.

BTW the higher speed and the smaller diameter both serve to increase belt creep so if you stay with the standard Linn belt this will dominate over the motor variation.

[IZHAKKATZ]

Hi Mark,

Would the controler work with with a Maxon A-max 7W 6 nominal V motor type 110182 ?

Thanks
I

[Mark Kelly]

Originally posted by IZHAKKATZ
Hi Mark,

Would the controler work with with a Maxon A-max 7W 6 nominal V motor type 110182 ?

Thanks
I

No, the motor voltage is too low, you would need to run it at around 250mV for 300 rpm.

[Vinyl-Addict]

Originally posted by Mark Kelly


We haven't yet decided on what to do as the "standard" pulley - I was going to ask Vinyl Addict to look at this. I would encourage the use of a tape belt as they will give better performance than a rubber belt.

I have made a custom cutting tool to machine crowned pulleys. The widest belt it will accept is 5/16" (8mm). It works perfectly with flat rubber belts, however I would like to try using a mylar or tape belt but have no source. I will probably have to machine a different profile pulley for the mylar belt.
Has anyone made their own and if so can you provide me with the information I need to make my own. I need a belt with a circumference at least 44".

I am currently using a flat rubber belt from Turntable basics. It is inexpensive at $10 and readily available. #FRM 38.8
I can machine pulleys for the Maxon 110191 motor or any Maxon motor with a 3mm spindle. It is somewhat of a challenge to make pulleys for any other mounting plate than my own design because the shaft of the motor doesn't extend very far. If anyone needs a pulley, they can go to Maxon's site and download the PDF engineering doc. and you can see what limitations you are dealing with.

My current setup is: 12.240" platter driven by the Maxon #110191 motor and 0.430 diameter crowned pulley. This allows the motor to run at approx. 949 rpm @ 33 1/3 and 1,280 rpm @ 45 rpm.

[superhkm]

Hi Mark, I have a no-name DC-motor running on a 12V Led-battery
driving a 320 mm Scheu platter (80mm heavy) with a plastic pulley taken of a toy car. Not satisfactory.

I would be interested in PCB with Deluxeparts and a pulley.

Can you recommend a DC Motor that would fit this setup and run on 12v ?

best regards hk,
vinyl collection still growing after 25yrs.

[Mark Kelly]

Originally posted by superhkm

Can you recommend a DC Motor that would fit this setup and run on 12v ?

Both of the Maxon motors I mentioned will suit. The 226764 will give better performance at 300 rpm but will require a 35mm diameter pulley for 33 1/3 RPM. The 110191 would allow you to use a smaller pulley or run both 33 and 45 rpm.

[fortytwo]

I am ultimatly intrested in a pcb. I have most of the other parts avalible. As long as a parts layout and list is included. It would ultimatly me helpfull if this was provided for both simple and complex versions.

As for motors i did some checking with maxon in the us and got some numbers. They have a minimum order of 205 dollars. for ordering a quantity of 1 - 4 it would costs 106.70 each for 5 - 19 it would costs 83.90. this is for 110191 .

IF someone else can get it cheaper let me know, i would also be intrested in a pulley, i do plan on running this at 33.3 and 45 rpm.

I have a question, I have a neat power brink from an old apple laptop i wanted to incorperate into the design of the moter controller. Mostly because it is round and clear. IT puts out 24 volts and 1.8 (i think) amps. Is there a simple circut someone could point me to that would drop the voltage down to the required 18 volts for this controller. and or should i just build a battery powersource with a charging / on switch. I have an old ups with 18 gel batterys i could use (and I am willing to sell the rest if anyone is intrested)

Thanks for even reading all of my rantings
Ed Owens

[Mark Kelly]

Originally posted by fortytwo
I have a question, I have a neat power brink from an old apple laptop i wanted to incorperate into the design of the moter controller. Mostly because it is round and clear. IT puts out 24 volts and 1.8 (i think) amps. Is there a simple circut someone could point me to that would drop the voltage down to the required 18 volts for this controller. and or should i just build a battery powersource with a charging / on switch.

Ed Owens

There is no need to drop the 24 volts to 18, it just means that the preregulator will dissipate more power and therefore require more heatsinking. Since the next stage is a CCS set to around 200mA the preregulator is well inside its limits, it can be fed with anything up to 36 volts.

I would encourage you to use battery power as I like it a lot. A very easy circuit to charge the batteries using your laptop power supply can be constructed for a few dollars using the excellent LT200C current limiting voltage regulator.

L200C datasheet

Figure 27 on the datasheet works, I use a slight modification but I'm not at my own computer at the moment so I can't post the details.