Opening up Bescor MP-101 Head

MP-101 Pan/Tilt Head patent makes for an interesting read.  Schematics in the patent depicts two H-bridges built from bipolar transistors.  And RF500T motors!  Are these Mabuchi RF-500TB?  Looks about right.  I now seriously think about opening the head and see whether I can discard all the electronics except the motors and have them wired to an existing DIN7 connector.  So that I could drive them both using a single TB6612FNG driver controlled by Arduino.  Hope to get more predictable results - love simplicity.

So, here is a perfectly working MP-101 head which I am about to disembowel...

After removing 6 screws you gain access to the electronics compartment.

The very first thing I noticed are those two ICs which look like LB1930 motor drivers.  This is fantastic because I now know which wires lead to the motors. It appears that yellow/orange wires lead to tilt motor and green/blue to pan motor.  Should I power the head up and see what voltage is used?  Never bothered to do that!

Here is a closer view with motor wires already unsoldered.


Few more screws and the PCB is released. I can see ST LM317T voltage regulator.

And the rest is just discreet elements.  Now, should I do something about those 45°, 90° and 340° end-switches?  Well, I tried.  But failed.

First note that there are no wires leading to +60 and +30 contacts.  Here are my notes on endswitch wire colors (note that in the photo colors are shifted because of the blue microscope light):
+60 - n/a
+90 - bluish-white
+30 - n/a
+0  - yellow
-0  - orange
-30 - green
-60 - brown ?
-90 - red

All these are neatly routed through a white tube:

Not only the +60 and +30 wires are missing, but I failed to discover how endswitches work.  It does look like my Bescor head was tampered - note other contacts missing - there are soldered points with no wires coming.  Despite being frustrated with time lost I do not mind it too much - I have now dirrect access to pan/tilt motors.  And after selling the remote with cable for $20 my cost is just $50 - I do not think I could remotely approach it with a DIY solution.

So my plan of action is to expose motors contacts via an RJ45 jack and to use regular CAT3 cable to connect the head to the controller!  Piece of cake!

Automated Video Slider with Pan/Tilt Head - User Interface Demo

Here is a short demonstration of the user interface. See previous posts for requirements and hardware details.

Automated Video Slider with Pan/Tilt Head - Hardware Design

In my approach to hardware design I will rely on the affordable off-the-shelf components.  Some of those components (slider or head) I already own.
Disclaimer 1: I am neither electrical nor mechanical engineer and I learn as I go.  And I love it!  I make mistakes and some of my statements could be wrong.  Feel free to correct me!
Disclaimer 2: This is a work in progress.  I think it should work.  But it might be proven to be otherwise.

Pan/Tilt Head

Instead of building a pant/tilt head from scratch (which is totally an option, given that I do not need tilt that much! well, maybe later), I will use Bescor MP-101.  It is almost affordable (I've got a used one for $80), adequately silent, and can be controlled externally, using Arduino's PWM outputs.  The head can be powered by 4xAA batteries, but external power connector is also available.  I intend to use the latter.
Parts:

• Connect head to the controller using 7-pin DIN cable.
• Power connector?? 5.5mm x 2.1mm?

Here are few sources related to use of this PT-head as a platform for application development:

• Chocolate Factory Pan Tilt USB Hack
• Bescor MP-101 Hack
• Bescor MP-101 Wireless Bluetooth Controller
• CamRanger PT Hub
• StackShot and CamRanger
• USB Pan Tilt Controller with Sony LANC (S-Link) interface

Slider

I already own a cheapo slider from Craigslist, which looks something like this.  EDIT: Found it!  This is Glide Gear DEV 1000.  For now this should do it.  I intend to motorize it.  I suspect a (cheap) stepper motor will be too jerky and/or loud which is not good for video shooting.  Therefore I decided to go with a DC motor. This also means that the position of the carriage will be unknown and its movement speed will be hard(er) to control.
Parts:

• 12V DC gearmotor 12RPM. Shaft 4mm
• Motor mount - to be designed.
• GT2 timing belt (6mm wide) with pulleys (20-tooth, 5mm bore).
• 15-tooth, 5mm bore pulley for GT2 timing belt
• TB6612FNG motor driver, datasheet, sample.
• 2x Endstop Switch.

Controller With Display and Keyboard

Parts:

• Arduino Mega2560 R3.  I decided to go with Mega as opposed to Uno because price difference is negligible and I do not mind extra size.  Room for growth is always nice!  However if all you want is to control the Bescor head alone, Arduino Uno should suffice.
• Proto Shield.  I plan to use this space for slider motor driver.  Maybe other parts.
• I strongly believe in the need for appliances to have GUI. This seem like a no-brainier:  Keypad LCD 1602 shield.  I wish the keys were arranged better and the reset button was less prominent.  Alternatively maybe 20x4 LCD display paired with Nunchuck with WiiChuck adapter would be a better option?  For now I will stick with the 16x2 LCD/keypad shield and will just rip the reset button and the power LED - it is way too distracting for my comfort.
• Connect to WiFi via ESP8266.  For now let's just leave it at that.

Power

I need 12V to drive slider motor - adjust the voltage to make sure sliding is slow enough.  6V to drive the Bescor PT head - adjust the voltage to make sure the panning is slow enough.  7V to drive Arduino and 3.3V to drive WiFi board.  I think 12V, 5A DC should be more than adequate and 5.5mm x 2.5mm power connector will do the job.  This remains to be proven though.
Parts:

• 12V 5A AC power supply connected to controller via
• 5.5mm X 2.5mm DC power supply socket.
• For powering the PT head or even Arduino I might use this DC-DC step-down module.
• Battery power.  I can go with a cheap 12V battery pack.  Alternatively Sony NP-Fxxx compatible batteries are readily available and, most importantly, I already own a few to power LED lights.  In this case I will also need a plate and DC-DC voltage booster.

That's it folks!

Automated Video Slider with Pan/Tilt Head - Requirements

Being a one-man shop I often wish I had an extra pair of hands to control the second camera.  Usually I set such a camera with a wide-angle lens trained at the event audience.  To add life into the footage some panning and sliding are highly desirable.  I am thinking most of the time this task can be fully automated!
Let's call this automated slider with pan/tilt (possibly zoom) head a camera control system.  Or the system for short.

High Level Requirements

• Once setup, the system should be capable of operating fully autonomously, with no operator involvement for at least 2 hours.
• Operator will be able to program the system. The program/script will reside in a separate file which can loaded/saved or created on the fly.
• The script will contain instructions like these:
• Rest 5 secs
• Pan left 20°
• Rest 15 secs
• Slowly pan left and slide left for 5 secs
• Camera control script requirements will be spelled out separately. Including:
• Operations supported include pan/tilt/slide/zoom/rest.  
• It should be possible to run operations in parallel or in sequence or in a loop.
• Operation arguments will be in time units or angle or distance units.  
• Operation with no argument may have qualifier, e.g. fast or slowly.
• Exceptions such as a slider reaching a limit or boundary should be supported.
• System should be scalable in terms of its capabilities.  E.g. it should be possible to use automated slider without automated Pan/Tilt/Zoom head.  And it should be possible to use the automated PTZ head without the slider.  Similarly the script created for a long slider should be usable on a smaller slider.
• System should tolerate power interrupts.  Ideally, once the power is restored, system should continue execution of the script where it was interrupted.
• Power supply should be modular, so that both battery and AC power are supported.

Constraints

• System power supply should be modular, so that both battery and AC power are supported.
• System will be built from the readily available of-the-shelf components.  Integration level of such components should be as high as possible.