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04-28-2014, 02:21 AM   #1
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Power of K3 Screwdrive motor

So, I was just wondering if anyone had a definitive figure for the power which the K3 screwdriver motor produces?

04-28-2014, 02:27 AM   #2
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It may be OT but:

P=U*I (Power in watts = Voltage * Current)- just find these 2 variables.
04-28-2014, 02:33 AM   #3
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Jeez, I'm really out of the loop when it comes to physics, but now that you've mentioned, I feel stupid
04-28-2014, 02:39 AM - 1 Like   #4
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It's up to 50% faster than motors in other cameras- I think that's a more relevant figure than whatever the tech specs may be.


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04-28-2014, 02:45 AM   #5
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QuoteOriginally posted by Adam Quote
It's up to 50% faster than motors in other cameras- I think that's a more relevant figure than whatever the tech specs may be.

Adam, I would generally agree with you, as for most users with experience with Pentax cameras, a 50% increase would be a useful comparison. But I'm actually interested in knowing if the K3 motor produces enough torque to drive the autofocus of 645 lenses(via a non-existent adaptor)
04-28-2014, 02:49 AM   #6
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QuoteOriginally posted by Joshua A Quote
Adam, I would generally agree with you, as for most users with experience with Pentax cameras, a 50% increase would be a useful comparison. But I'm actually interested in knowing if the K3 motor produces enough torque to drive the autofocus of 645 lenses(via a non-existent adaptor)
Why - are you going to create the adapter?
04-28-2014, 02:52 AM   #7
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QuoteOriginally posted by DSims Quote
Why - are you going to create the adapter?


Would I ever love to. Mechanically, I have the tools available to fabricate the adaptor at home, and my skills are relatively advanced with electronics. But I don't know if this lies within my field of knowledge.
04-28-2014, 02:53 AM   #8
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QuoteOriginally posted by Joshua A Quote
Adam, I would generally agree with you, as for most users with experience with Pentax cameras, a 50% increase would be a useful comparison. But I'm actually interested in knowing if the K3 motor produces enough torque to drive the autofocus of 645 lenses(via a non-existent adaptor)
You'd have to check this, but it's quite likely that the 645D uses the same AF motor as the K-7, as with most of the other hardware. So in theory the answer is most likely yes. It would be hard convert the 645 mount contacts to the K-mount contacts, however, let alone trick the camera into treating the lens as an AF lens.


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04-28-2014, 02:55 AM   #9
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QuoteOriginally posted by Joshua A Quote
Would I ever love to. Mechanically, I have the tools available to fabricate the adaptor at home, and my skills are relatively advanced with electronics. But I don't know if this lies within my field of knowledge.
Well, make sure to show it off here if you ever do create it!
04-28-2014, 02:57 AM   #10
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QuoteOriginally posted by Adam Quote
You'd have to check this, but it's quite likely that the 645D uses the same AF motor as the K-7, as with most of the other hardware. So in theory the answer is most likely yes. It would be hard convert the 645 mount contacts to the K-mount contacts, however, let alone trick the camera into treating the lens as an AF lens.


That's actually the problem with even thinking about conversions, is that at the heart of it, cameras are simply computers, and without knowing the exact protocols that the use, it is difficult to design things, such as adaptors and accessories, to work with the said camera.

---------- Post added 04-28-14 at 07:29 PM ----------

QuoteOriginally posted by DSims Quote
Well, make sure to show it off here if you ever do create it!


If I did ever design and build something like hat, this would be the first place I would go, and then if try to profit off it!
04-28-2014, 03:01 AM   #11
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QuoteOriginally posted by AldaCZ Quote
It may be OT but:

P=U*I (Power in watts = Voltage * Current)- just find these 2 variables.
Caution is advised with using this equation, which is true for conventional Direct Current (DC) motors. The drives used in cameras tend to be pulsed, to allow for digital control, so if we assume a square wave pulse, the average voltage will be half the nominal rating (peak), as will be the current.

We still don't know what the "DC" drives in the DA 18-135 and the DA 20-40 are (the SDMs are piezo-electrics, I understand), but I'd be highly surprised to find they were conventional DC motors, which aren't the best drives for fast digital positioning control duties. DC stepper motors are the norm for heavier duty applications of that type.
04-28-2014, 03:03 AM   #12
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Adam is probably right, the motor must be the same between K-7 and 645D sd they were developed at the same time (same AF system, processor, screen, probably same af motor). But even if the 645D motor was more powerfull you could still use the K-3 motor with the proper combination of gears, resulting in a slower speed to get the necessary torque.
This is actually a good idea as you will just need to short circuit 2 contacts to get the AF system running on the body. The diffcult part will be finding the space to place the gears between body and lens mount.

EDIT: Actually, there seems to be some space available:
04-28-2014, 03:06 AM   #13
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QuoteOriginally posted by RobA_Oz Quote
Caution is advised with using this equation, which is true for conventional Direct Current (DC) motors. The drives used in cameras tend to be pulsed, to allow for digital control, so if we assume a square wave pulse, the average voltage will be half the nominal rating (peak), as will be the current.

We still don't know what the "DC" drives in the DA 18-135 and the DA 20-40 are (the SDMs are piezo-electrics, I understand), but I'd be highly surprised to find they were conventional DC motors, which aren't the best drives for fast digital positioning control duties. DC stepper motors are the norm for heavier duty applications of that type.


Well, that is strictly true, but I wouldn't want to be even touching the SDM or DC lenses, as they're too expensive to play around with

---------- Post added 04-28-14 at 07:38 PM ----------

QuoteOriginally posted by carrrlangas Quote
Adam is probably right, the motor must be the same between K-7 and 645D sd they were developed at the same time (same AF system, processor, screen, probably same af motor). But even if the 645D motor was more powerfull you could still use the K-3 motor with the proper combination of gears, resulting in a slower speed to get the necessary torque.
This is actually a good idea as you will just need to short circuit 2 contacts to get the AF system running on the body. The diffcult part will be finding the space to place the gears between body and lens mount.

EDIT: Actually, there seems to be some space available:


I personally think that the space given between the Kmount flange and the 645 mount is extremely generous, and I can't believe that pentax hasn't built an adaptor already so their lens selection is boostered
04-28-2014, 03:09 AM   #14
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QuoteOriginally posted by carrrlangas Quote
Adam is probably right, the motor must be the same between K-7 and 645D sd they were developed at the same time (same AF system, processor, screen, probably same af motor). But even if the 645D motor was more powerfull you could still use the K-3 motor with the proper combination of gears, resulting in a slower speed to get the necessary torque.
This is actually a good idea as you will just need to short circuit 2 contacts to get the AF system running on the body. The diffcult part will be finding the space to place the gears between body and lens mount
It would make an excellent engineering student design problem. The radial and angular locations of the body drive and lens coupling axes are the important parameters, and then it becomes a matter of which type of drive is best. Pinions and ring-gears are the likely candidates, with the challenge there being the ring-gear locating method. Space shouldn't be a big issue with that system.
04-28-2014, 03:11 AM   #15
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QuoteOriginally posted by RobA_Oz Quote
Caution is advised with using this equation, which is true for conventional Direct Current (DC) motors. The drives used in cameras tend to be pulsed, to allow for digital control, so if we assume a square wave pulse, the average voltage will be half the nominal rating (peak), as will be the current.

We still don't know what the "DC" drives in the DA 18-135 and the DA 20-40 are (the SDMs are piezo-electrics, I understand), but I'd be highly surprised to find they were conventional DC motors, which aren't the best drives for fast digital positioning control duties. DC stepper motors are the norm for heavier duty applications of that type.
Thanks for the reply!

Im curious what kind of motors is used in cameras. PWM , I thought is has to be fed by one.
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