merlin voltage vs speed  

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wjh31
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merlin voltage vs speed

by wjh31 » Sat Jan 08, 2011 9:58 pm

I thought i would have a look into how voltage supplied to the merlin head effected the speed, as various posts here indicated it should make a difference, so i carried out some tests to compare the performance with 8xAA NiMH (9.6V) vs a 12V supply from mains. Controlled with the N800 two tests were done with each supply, one at 500mm to test fine movement, one at 50mm to test larger movements, both times an appropriate lens and body was mounted. A 10x10 grid was shot under each configuration shooting columns, i.e an up/down configuration as in landscape this gives the shortest movement between images. Results were supprising to me:

500mm:
12V - 15:46
9.6V - 15:43

50mm:
12V: 21:30
9.6V: 20:11

There is no significant difference in the speed despite a 25% increase in supplied voltage. Am i doing something wrong or were other peoples comments just speculation? Has anybody else carried out similar tests with different results?
Last edited by wjh31 on Sat Jan 08, 2011 11:02 pm, edited 1 time in total.

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by fma38 » Sat Jan 08, 2011 10:51 pm

I'm always suprised to read that the power supply changes the speed, as in my initial tests, when I got the Merlin, I found that at full speed, the motors where only powerd up with arround 5V by the PWM. So, in theory, we can reach the full speed with a 6-7V power supply.
Frédéric

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by donpesce » Sun Jan 09, 2011 1:54 am

I thought the speed increase would be when operating at 15V. The Merlin head officially supports 11V to 15V. But actually i've never tested it out since my head is not ready yet.
Nikon D80 --- Sigma 8mm f4 EX --- SIGMA 10-20mm F/4.0-5.6 EX DC HSM --- Pano-MAXX --- Manfrotto 055XProb --- IR- & Funk/Kabel Fernbedienung --- HUGIN --- Krpano

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by fma38 » Sun Jan 09, 2011 9:37 am

As I said, the motors are not powered up directly from the batteries. There is a PWM (Pulse Width Modulation) before a H-bridge, in order to be able to change the speed of the motor. This speed is controlled by reading the encoders. And to reach the full speed, the motors only need 5V. The only difference will be the ratio of the PWM, changing with the power supply.

This is also why you get the same speed over different voltages. Without it, the speed would continuously decrease while the voltage decreases...
Frédéric

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by claudevh » Sun Jan 09, 2011 11:40 pm

Hello All,

I have made several speed test with different Power supply voltages, and I can certify that the speed increase with the voltage !
This increasing isn't linear (= not directly related to the PSU)
The effect of the PSU voltage also depend of the firmware version ... for some firmwares the increasing is more spectacular !
This has also be confirmed by other users and by the users of the " T & C controller TouchCP(FW 2.0)" ...
:cool: Claude :cool:
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Gigapixel photography with Nikon D200 + Sigma 70-200 F 2.8 EX DG APO HSM

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by fma38 » Mon Jan 10, 2011 7:01 am

Don't you think this is more a current limitation rather than a voltage limitation?

It may also occurs if the camera is not balanced; in this case, the PWM will need to increase the ratio to boost up the motors... Did you make tests without any load?

To be sure, one should use a power supply with the current and voltage limitation and feedback, to see what exactly happens.
Frédéric

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by claudevh » Mon Jan 10, 2011 10:05 am

Hello Frederic,

I don't know if we have a "current limitation" or a "voltage limitation" ...
This should be investigated further !
We think that we know all concerning the Merlin, but this is not true !!! :lol:
:cool: Claude :cool:
Merlin + Papywizard on Windows 7 & Nokia 770 § N810 & Acer (Netbook) + PanoramaApp Androïd + Deltawave PapyMerlin BT + Autopano
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Gigapixel photography with Nikon D200 + Sigma 70-200 F 2.8 EX DG APO HSM

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by Greg Nuspel » Tue Jan 25, 2011 2:14 am

What is the speed of the Merlin? My head takes 40 seconds to do a 360 turn, in other words 9 degrees per second, how does that compare?
--Greg Nuspel

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by josefgraessle » Thu Feb 17, 2011 2:05 pm

By accident I found your discussion subject. You are all right in some way. I analysed the speed at different voltages (9.6V 12V and 15V) and found if the controller (Nokia or T&C) uses the GOTO command to position the head there will be no speed difference related to the voltage. I assume that the firmware of the head is controlling the speed independently of the voltage at the GOTO command. The GOTO command is in the T&C controller only used for moving angle of less than 10 degree. That means for sensorsize 36x24 (fullformat) and 20% overlapping above a focallength of 163mm or 109mm depending on portrait or landscape. And for a sensorsize 22.8x14.8 above a focal length of 109mm or 67mm. Below does the T&C controller run the head by MOVE command, where the speed is controlled by the controller and not by the head. With this I run the following tests:
Nikon D700 (36x24mm sensor) full panorama f=24mm 28 pictures 15.5V -> 219s 12V -> 269s 9.6V ->327s that means an speed difference of almost 50% between 15.5V Lithium and 9.6V NiMh. The next test was with f=200mm 5X5(25) pictures. The result was 240s independent of the Voltage.


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