Sunday, March 15, 2015

The New Timelapse Slider - the Electronics

This was the hardest part for me. The previous slider had just constantly turning 1,5m long screw to drive the trolley, no integration with camera shutter. And had a hard limitation to approximately 2 hours of trolley slide.
So this time it is different: the device should operate in shoot-move-shoot style. So it needs a special driver that will manage the shutter actuations and synchronized trolley movements.

After some weeks of testing and development based on Arduino Uno R3 board

I have constructed a driver that includes:
- 16x2 characters LCD display (WH1602B, compatible with HD77480) + PCF8574 + 3 operating buttons;
- voltage regulator L7812CV that assures constant 12V DC voltage delivery to the motor (from the 14-18V input);
- output to camera shutter (on the plate it is just a 10K resistor to the ground);
- 2-channel motor driver (only one channel is used in my case) L293DNE.

The almost finished electronics

The Failures and Obstacles

Everything was fine until the circuits were on the prototype board and I don't start final soldering.
The first "catastrophe" happened when I by an accident just touched some pins of LCD by 18V wires. So the first Arduino went dead. The lesson: be always extremely careful with not isolated cables!
The second accident was when I wanted to solder again L293DNE. This took too long, and I must have damaged circuits inside the chip .The result was the second dead Arduino board :-(
The lesson learned: solder dedicated bases, not the chips!
After this accident I just thrown away all the components and used brand new ones (except LCD).

The last issue occurred hen I soldered my circuits and then the LCD started going crazy short time  after the motor ran.

This is how I like it...

... and this is how I don't like it.

I assumed that this was caused by reverse electric noises from the motor and I was right. I soldered two capacitors between motor outputs and the ground. This helped instantly.
Finally the capacitors are not used, because in the third Arduino and third plate the phenomenon does not occur.

Here the final schematics:

1 comment:

  1. A very professional look at a Timelapse Slider. Good to see the obstacles you have encountered and how you overcame these as I have damaged circuits before. It's nice to see I'm not the only one. Schematics look great and I am particularly impressed that you have included so many characters on the display.

    Raymond @ CKS Global Solutions LTD