Arduino Watchdog Timer
The watchdog timer will automatically cut power if the watchdog app
running on the PC fails to send keepalives. This protects against
the monitoring PC failing for some reason. Without the PC present to
monitor the mount position the watchdog will automatically cut power
to the mount to prevent it tracking past safe limits.
Parts List
| Item | Source | Approx. Cost | Notes |
| Arduino Uno R3 | newegg.com | $5.50 | |
| 4-Channel Relay Module DC 5V For Arduino | ebay | $6.00 | |
| 9VDC power supply for Arduino | ebay | $6.00 | |
| on-off toggle switch | ebay | $5.00 | |
| Arduino jumper wires M-F | |||
| Wires and connectors for mount power cable | I used Anderson Powerpole connectors and 18 AWG wire. | ||
| Enclosure | I used a PVC electrical junction box |
Assembly
The Arduino program is here.
Make sure to use the NO (Normally Open) terminal of the relay so that the mount does not receive power until the watchdog is activated.
After connecting everything together and testing it, secure the Arduino and the Relay module in an enclosure. I used an ordinary PVC electrical junction box from the local home improvement store. The toggle switch is available in case there is ever a need to bypass the watchdog timer.
Andy Galasso 5/2015
andy.galasso@gmail.com