$35 Wireless Follow Focus From the Crane 2

Let's make a $35 wireless follow focus for your camera. This can be great for use on film sets with a dedicated focus puller and can be used to adjust the zoom or focus of any camera wirelessly.

Soldering Iron and solder

Heat Shrink

Courage and a will face the opportunity to diversify your skills

Find a Crane 2 Follow Focus Servo from ebay (I found a few for under $30 that were being resold). If you have a gimbal with a servo already don't worry this hack is non-invasive and will not affect the normal operation of your gimbal!

It is highly recommended that you upgrade your servo's firmware to at least V1.70 to make use of the Stop A, Stop B and Clear functions of the application. More information on how to upgrade the firmware can be found on the official ZhiYun Crane support website. You will have to plug it into your computer to do this.

We need to gather only two (or three) more pieces for this build:

- HM-10 Bluetooth LE (low energy) serial communication device [these are extremely cheap as well]

- a pack of two micro USB connectors (preferably right angle or 'down-angle')

The default BAUD rate of the HM-10 is 9600 bit/s. We need to change the BAUD rate to 115200 to be able to send commands to the focus motor. Plug your HM-10 into a UART to USB adaptor and use the Arduino serial interface to change the Baud rate using the following commands:

1. AT

(should respond with an 'OK')

2. AT+BAUD4

(should respond with an 'OK+get:4')

Disconnect the HM-10, thats all we had to do!

The bottom port will be used to inject the TX serial data to the focus motor. We need to solder a lead from the TX port of the HM-10 to pin 4 of the micro USB male connector (usually is not frequently used for things). This pin should be right next to the ground pin. This connector will be plugged into the bottom of the focus motor that is labeled 'Crane 2'.

The USB Port on the left supplies a low current +5v supply that we can tap into to power our own HM-10 so we will splice a second wire to another microusb connector to pull 5 volts and a ground reference to the HM-10. (see images).

Hint: Use Heat shrink to couple the wires together so they can stay together well during use!

UPDATE::::::::::::::::::::: PLEASE SEE CORRECTION PHOTO FROM THE COMMENTS, THE WRONG PIN NUMBER FOR THE TX PACKETS WAS LISTED IN THE VIDEO, SORRY ABOUT THAT!

Plug the USB ports into your follow focus motor and velcro the HM-10 module to the backside.

I have created an application to drive the command packets through Bluetooth for the motor to listen to. This includes functionality for A and B stopping points as well as a sensitivity and reverse direction options. Check out the link (link below) to drive your motor using an android device running Android 5.0 or later!

Free App:

https://play.google.com/store/apps/details?id=appinventor.ai_ouch3994.ARD_HM10_AI2_Single_LED_03&hl=en

I apologize, i had started a new job and was have had little time to check for comments. I forgot to attach some code... i think this one was working, you will have to inject the arduinos output into the bottom USB port. this code makes the packet and attaches a CRC onto the end of it and transmits every 20ms as observed... i think i had a basic rotary encoder working too with this one. you will need the two libraries installed if you want this code to work for you...

'Encoder' https://www.arduino.cc/reference/en/libraries/enco...

and

'FastCRC' https://github.com/FrankBoesing/FastCRC

Hex string to send for:

Set A stop: [A5 5A 45 71 40 E0 02 00 87 E1]

Set B stop: [A5 5A 45 71 40 E0 03 00 B6 D2]

Clear stops: [A5 5A 45 71 40 E0 04 00 21 4B]

This already has the appropirate CRC included at the back of the listed packets

send one of these in place of a normal packet of data in the interval if you want to command the end A/B stop functionality of the motor.

You will need to purchase a second HM-10 and put it in Master Mode, and command it to connect to the MAC Address of the Slave HM-10 (on your motor). Grab a cheap rotary encoder and a potentiometer to make the wiring diagram above and have a stand-alone wireless follow focus!

post questions if needed!

-jack 4/1/2022

working out the kinks on making a bluetooth controller so you dont have to use the app... using a rotary encoder and another HM-10 module. Will update when i get the chance.