DC Motor for DIY 16mm Telecine?

[electrodist]

Thanks for all your suggestions. I will post my results on the thread.

Frank, can you post that URL for the motor again? All I get in Safari is a timeout page for rswww.com

[RCBasher]

Try this for the manufacturer: http://tinyurl.com/ypojum I have the -35 model.
For the supplier, go to http://www.rswww.com and enter code 512-6012 in the search box. For some reason, even though not logged into their site, they seem to run sessions which time out.
Word of warning in advance though....they are not cheap! UK123.16 + tax

[electrodist]

Wow, with the current exchange rate that's about $260US! Not a good time for Americans to purchase British goods.

Thanks Frank!

[JhnZ33]

Wow, with the current exchange rate that's about $260US! Not a good time for Americans to purchase British goods.

Thanks Frank!

Exactly why I can't take the leap right now. That's a big chunk of change to drop for me - PLUS SHIPPING!

John

[RCBasher]

Agreed! The price hasn't changed here while the $ has been diving...but that doesn't help you guys. But perhaps the datasheet might help you to find something similar US based?

Good luck!

[JhnZ33]

Here's something worth taking a look at. A little overkill for the application, but with some new pulleys, a decent power supply and good PWM controller it could certainly work. Best of all it's a whole lot cheaper!

John

[VideoFred]

I bet that Bosch motor was original made for the car or the truck industry. For those on a low budget: look for a second hand car parts supplier!

Todays car industry must have build millions of all kinds electromotors. With all these automatic functions in today's cars... All very reliable motors, all low voltage... Thousands of those must be available in second hand car parts shops.. I got mine for 10 Euro's/each. It was the back window wiper motor from the Ford Fiesta model. The front window wiper motor was to huge for me.

Fred.

[JhnZ33]

Here's something worth taking a look at. A little overkill for the application, but with some new pulleys, a decent power supply and good PWM controller it could certainly work. Best of all it's a whole lot cheaper!

John

Well, I just purchased one of these motors. I'll let everyone know how it works out.

As for the light source, I use a 75W MR16 Halogen off the original power feed and fixture. This fixture originally pointed the bulb directly at the film gate. I removed it from the chassis and pointed it, facing down, into a small light chamber with a 45 degree bounce directed at the film gate. The chamber is made of wood and the interior is completely covered with white office paper. The output end (in front of the film gate) is covered with opal glass, purchased from Edmunds Optics. The result is a very soft and diffused 2" square light source.

I tried different watt bulbs, and 75 seems to produce the best image.

I'd love to see a photo of your lamp solution and your setup. I'm quite intrigued.

[JhnZ33]

Well, got the motor I suggested - MORE than enough torque! In fact, I hooked it up to a 12 volt drill battery and the damn thing took off across the table and hit the floor! Ripped the leads right off the battery!

Though the seller lists it as a 24 volt motor, 12 volts is printed on the case and I would guess at 12 volts it spins real close to 3900 RPM no load speed - which is a good speed for the application.

You will need to get a different pulley for the motor as the pulley from the AC motor has too large a center hole. But with a new pulley, a good 6 to 10 amp 12 volt power supply and a PWM speed controller, one should be all set.

The seller has many listed on ebay right now, and at $20.00 US (including shipping for me), it's a real bargain!

John

[electrodist]

So I put a BLY17MD2S from Anaheim Automations into the Eiki SSL-0. The motor is 24V and rated at 60W and 4000rpms. It is a brushless DC motor with electronic speed control built in. Connected to this are pulleys which give me a ratio of 2.78:1, which should be 24fps at 4000rpms.

Results: at full power the projector goes above 24fps. I don't know how much faster it is, but objects in the films are move faster than real life.
At the lowest holding speed (I'd say about 8 fps) the motor does not have enough starting torque and stalls on startup. This is because of the camtank gear requires a lot of force while it engages the claw pulldown. It will stay running if I physically help it make that first revolution.

So I think I am going to change out the pulley ratio to 5:1 to lower the speed, so I can work with this same motor. Do you guys think this would transfer the power and torque more efficiently? I could keep the motor at a higher power setting and achieve almost half the speed of the current configuration. Also, does anyone know if I can use a capacitor with a brushless DC motor to get more startup torque?

[/code]

[JhnZ33]

Hello electrodist, looking good.

So I think I am going to change out the pulley ratio to 5:1 to lower the speed, so I can work with this same motor. Do you guys think this would transfer the power and torque more efficiently?

Well you would definately gain some torque by changing the ratio, but you would also lower your max speed in the process. I don't know if you'll be able to achieve 24 fps with a 5:1 ratio. This is no problem if you are using this for frame-by-frame capture - in fact you don't want to go over 8 fps or so if you are using Cinecap or you'll start dropping frames. Roger could definately elaborate on this.

Also, does anyone know if I can use a capacitor with a brushless DC motor to get more startup torque?

Using a cap will not gain you any torque, either at startup or continuous running. Depending on the power supply being used, it may help smooth the load on the supply, but the difference may be un-noticeable.

John

[RCBasher]

So I put a BLY17MD2S from Anaheim Automations into the Eiki SSL-0. The motor is 24V and rated at 60W and 4000rpms. It is a brushless DC motor with electronic speed control built in. Connected to this are pulleys which give me a ratio of 2.78:1, which should be 24fps at 4000rpms.

Results: at full power the projector goes above 24fps. I don't know how much faster it is, but objects in the films are move faster than real life.
At the lowest holding speed (I'd say about 8 fps) the motor does not have enough starting torque and stalls on startup. This is because of the camtank gear requires a lot of force while it engages the claw pulldown. It will stay running if I physically help it make that first revolution.
[/code]

Hi, Something doesn't seem right :? . That 60W motor should easily do the job...is your power supply up to it? Is it a regulated 24V? How many amps is it rated at?

Cheers,
Frank

[electrodist]

I thought the same. The original motor was 37 watts. The power supply is a Cincon CFM60S240 which is a 24vdc 2.5amp so 60watt power supply. It is regulated and advertised as ready for medical use.

The motor has no problem at full speed. It has a 5VDC output and a 0-5VDC input for speed control. I am using a 5k-ohm linear pot rated at .5 watts between the input and output to change speeds. The lowest holding speed I can get is between 6-7 frames. The problem is on startup. The oddly shaped gear in the camtank that moves the claw requires much more force at the moment that initiates the claw pulldown. The gear doesn't create much mechanical resistance until this point in the revolution. At this slower speed the motor needs the tiniest bit of help on startup to get over this hump (really only sliding my finger across the manual frame advancing knob). And this is only if the startup position of the camtank gear is close to the moment of pulldown. Otherwise, the motor has enough of a running start to get over the load hump.

The only other component not described is the wiring-it is all 18 gauge wire alligator clips. Also the belt is tight but not completely taut. Would a very tight belt fit help to transfer power better?

Could it be my pot as well? I don't know much about resistance ratings. Again this one is 5kOhms. At the lower 1/5th or so of the power spectrum there is essentially no torque for the motor. I can stop the free shaft from spinning by simply putting my finger on it.

John, I will post a picture of the new lamp solution for you when I get a chance to snap a shot of it.

[RCBasher]

Do you have a multimeter to hand? If so, try measuring the supply during startup when the motor is stalled. Also measure the 5V output to check it isn't dropping and hence dropping the control volts. If you suspect that it is, then try a separate +5V supply for the pot. I wouldn't expect the speed control input pin to take much current at all. Make sure both ground pins (5 & 6) are connected to ground.

I have to say that the motor looks a bit skinny for the claimed 60W compared with 35W one I have, which is about 2.75" dia by 2.5" in length.
Dia. is what really counts when it comes to torque.

Finally, you may be on the edge with your PSU rating. If so, a big electrolytic may help with the startup surge.

Frank

[electrodist]

5 is connected to the third (side) lead of the pot. 6 is connected to the PSU V- output. Should these be grounded on the chassis as well? The PSU is grounded through screws onto the chassis metal as is the ground lead from the AC cord.

Out to get a multimeter.

Also, I started another thread about capture limitations that you brought up earlier in this thread John.


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