Summary of Remote key-switch operation Using Arduino
This article describes a remote-controlled key-switch activator designed for Dr. Shane Mayor's LIDAR atmospheric research system. To avoid altering the laser’s original power supply and preserving the warranty, the author created a servomotor key-turner that physically turns the key via a servo motor controlled remotely through a digital line from a National Instruments control board. The system uses an Attiny85 microcontroller programmed with a servo control library and mounted in a project box with a custom actuator to engage the key.
Parts used in the Servomotor Key-Turner for LIDAR System:
- Attiny85 microcontroller
- Servo motor
- National Instruments control board (for digital output)
- 6-pin ISP header (J1)
- Arduino board (used as ISP programmer)
- Rubber stopper actuator with a slot
- Servo control arm
- Custom etched PCB (using toner-transfer paper)
- Project box (scrapped box top for mounting)
- Servo8Bit library (software component)
One of my colleagues, Dr. Shane Mayor, has built a very nice LIDAR system for atmospheric research. It’s located at a remote site, at the end of a dirt road, and everything about the system can be controlled remotely except the main pump laser power supply. That supply has a key-switch, which has to be manually turned to activate the system. He asked me to see what I could do to make it all remote-controlled.
Due to the cost of the laser, and Dr. Mayor’s unwillingness to void the warranty, my suggestion that he just replace the key-switch with a computer-activated relay was met with some resistance. He absolutely did NOT want me to do anything inside that case! So instead, I built a servomotor key-turner.
The basic idea is to use one of the spare digital lines on his main National Instruments control board to signal the servo controller. When the line goes high, the servo turns the key to the ‘on’ position, and when the line goes low, the servo turns the key to the ‘off’ position. Any simple microcontroller should be sufficient for the task: rather than commit an entire Arduino board to the job I just used an Attiny85. Still overkill, but it’s so cheap that I don’t stock anything cheaper in my parts bin anymore!
Here’s the circuit:
And here’s the board, which I etched using Pulsar’s “Fab-in-a-box” toner-transfer paper.
The software uses Ilya Brutman’s Servo8Bit library, and I programmed the Attiny85 using MIT’s High-Low Tech instructions. Here’s my code. There’s a 6-pin ISP header on the board (J1), which I use with an Arduino-as-ISP programmer.
I used the top of a scrapped project box to mount the servo directly above the key and hold the servo output shaft coaxial with the key. The actuator consists of a rubber stopper with a slot cut in it, mounted on a servo control arm. The slot in the stopper fits over the key so that the servo turns the key directly.
For more detail: Remote key-switch operation Using Arduino
