Joined: Tue Aug 17, 2010 10:12 pm
Posts: 31

Alternative to Merlin Head for MX2? Bescor MP-101/MP-360

Hi guys, I have been (as many of you might as well) trying to buy a Merlin Head, but it is often out of stock or difficult to ship out of Europe (I am in Mexico) without expensive shipping costs.
I found the Bescor MP-101 http://www.amazon.com/Bescor-MP101-Video-Motorized-Head/dp/B0000AUR21/ref=wl_mb_hu_m_5_dp and MP-360 http://www.amazon.com/Bescor-MP-360-Motorized-HDslr-Cameras/dp/B00535TL0M/ref=sr_1_3?ie=UTF8&qid=1344913451&sr=8-3&keywords=bescor+head on Amazon, and they seem cheap and sturdy, with some pan & tilt limitations, but might be able to operate with the MX2.
I found this thread on the Bescor MP-101 http://forum.timescapes.org/phpBB3/viewtopic.php?f=24&t=4872 that explains how it can be hacked to pan 360 degrees, and how to wire it in order to communicate with the MX2 (although a bit more info on how to proceed would be appreciated).
I bet that if someone can come up with a diagram on how to build an MX2-compatible cable to communicate with these heads and how to set up the MX2 for controlled moves, they would be a great option for 3-axis time lapses, combined with the Dynamic Perception dollies.
Any thoughts on this motorized heads?

Joined: Wed Nov 11, 2009 10:45 am
Posts: 1685
Location: Merritt Island, Florida, Estates Unitas

Re: Alternative to Merlin Head for MX2? Bescor MP-101/MP-360

I like your avatar picture. What is the big cloud behind the truck? It looks like the back doors swung open and 100 million dollars of coke is blowing out, or its the biggest dust devil in the world.
First thing you need to understand is these pan/tilt heads are not a replacement for the Merlin or other telescope drives. The MX-2 is a two axis motor controller, meaning it can control two DC motors. One motor can control your dolly and the other can control ONE other axis so you can coordinate a focus motor or a pan with the dolly move. Dynamic did some very impressive magic to let it control the telescope head by using a different method of control entirely. If you have the telescope drive plugged into this other port, you still have two useful motor ports, so you could do a dolly/pan/tilt/focus shot with four useful axes. Paying me to build you a controller to run the Bescor from the MX-2's telescope interface would cost you more than just buying a different MOCO system off the shelf that runs four axes.
If you need to run the Bescor from the MX-2, the easiest way would be to use the other motor port which is not running the dolly. Remember, this gives you a two axis system only.
The links on Amazon show the head with its remote control. They even have an optional extension cord for the remote. I'd recommend getting the extension cord and modifying it. That way you can keep your original remote intact. When you want to use it for regular video, the original remote works pretty well.
Assuming that your remote is wired like mine, there are seven wires coming out of the plug on the pan/tilt head itself. They connect to the circuit board inside the remote in the following order; purple, yellow, blue, white, black, green, red. The two outer wires (purple and red) go to the sliding potentiometer which controls speed. The center wire (white) is a common wire for the direction buttons. Yellow is left, blue is down, black is up, and green is right.
The simplest way to get the MX-2 to control the bescor head would be to use an electromagnet-relay switch to interrupt the common (white on my unit) wire from the remote. You want to use the normally open contacts on the relay switch so that electricity only passes when the electromagnet part is ON.
To do this trick, you have to use the MX-2 in Shoot-Move-Shoot mode (Fixed Interleave Mode).
This tells the MX-2 to apply full power to each motor output for an amount of time determined by how far you tell it to go. You get an electromagnetic relay where the electromagnet is made for 12 volts DC. Wire the electromagnet leads to a barrel plug which fits the MX-2 motor output. (beware, the correct plug is NOT the same as the plug for 12v power into the MX-2, although they look identical and it fits into the socket. You'll get no electricity or intermittent if you use the wrong plug) Now when the MX-2 tells that axis to move, the swtich part of the relay should close momentarily. If you have it move farther, the switch should close for a slightly longer time.
If you attach the common (white on my controller) wire to one side of the relay switch, and the wire corresponding to the direction you want the Bescor to move, to the other side of the relay switch, then the motor should move a bit whenever the MX-2 turns on the relay's electromagnet. If that makes sense to you, then you can probably make it work. It would help a lot if you have a multimeter or some way to see if electricity is flowing at different points in the circuit so you can figure out any problems as you go. Thats the simplest way to run it. You could literally have a wire coming off the relay and just twist the direction wire onto it to select a direction. You could even have the Bescor move diagonally by twisting the up and right wires on for example. Its probably bad to connect both left and right at the same time for example.
At this point, you might think about getting a couple of double-pole-double-throw switches and wire them so you can select 'left-off-right' with one switch and select 'up-off-down' with the other.
So thats how I'd do it. If you don't have much money and don't mind the limitations, its pretty inexpensive and works with a controller you already own. Remember, the stage zero dolly and MX-2 controller were meant to be an inexpensive timelapse-only dolly system with approximate control. It was never meant to go fast enough for regular video. It was never meant to do precise, repeatable moves. It was meant to cost less than half as much as anything available when it was designed. Its a crying shame Celestron discontinued the Merlin as soon as the interface for it was ready. Even worse, they trashed the control system and made something incompatable with it on their new drive.
If you've got money, I'd go with something else. eMotomo is a great pan-tilt head and several Timescapes members have converted their stage zero dollies to stepper motors so the eMotimo can control a dolly/pan/tilt shot. If you're going to convert the dolly to stepper motor drive, it could be used with Mantis or Dragonframe controllers or even Dynamic's new Nanomoco control system when its ready. These are all much more capable systems which can do repeatable, precision moves. Mantis can run realtime and timelapse moves. All will be able to control more than the three axes you'd get from eMotimo or the two you get with the MX-2. Dragonframe can control four axes as far as I've heard, and I think Mantis can do eight. Nanomoco can control an unlimited number of axes, lights, cameras, and who knows what.
I can build you a motion control system around any of those other controllers. It would do precision repeatable moves and control any hardware you need controlled, for example focus, zoom, filter changer, pan, tilt, roll, dolly, and even crane up-down-pivot if necessary. It could use your stage zero dolly as the dolly track and trolley to save money on the build if you want.