Jeffrey Warren has extensively investigated using 555 circuits to trigger cameras via CDHK.  This appears to be the least expensive option, [his notes are here](/wiki/dual-camera-kit-electronics).  for completely DIY 555 circuits, [see Mathew Lippincott's note here](/report/adjustable-555-based-shutter-trigger-circuit).


Cris Fastie has explored two other options providing greater degrees of control:

1) using a tiny remote control purchased on ebay. [his notes and KAP forum discussions here.](/notes/cfastie/4-22-2012/tiny-remote-control)

2) using an [AuRiCo](http://skyware.fam-engels.de/), or AutoRigController, [sold in the states by Brooks Leffler](http://skyware.fam-engels.de/).  His notes are [here](/notes/cfastie/4-10-2012/almost-synchronous-shutters) and [here](/notes/cfastie/4-14-2012/good-shutter-synchronization)