Author:  Mike Boesen

Last updated: 24 July 2006

1.  Background

I wrote an article recently about backup strategies.   In the article I referred to the merits of using a hard drive in a removeable caddy as a backup device.  The "caddy" is a removable container in which a hard drive is kept.  The caddy slides into a "cradle" (or "rack") that is mounted permanently in one of the CD or DVD drive bays in the PC.   The caddy containing the hard drive can be completely removed from the cradle.  This setup is also referred to as a "mobile rack" but this is a misnomer - what is mobile is the caddy;  the rack is fixed in place and is not mobile.  

In another article I described some ways of modifying a particular Laser brand caddy to improve aspects of its architecture.  One of the modifications I suggest involves installing a microswitch so that the fan in the cradle only comes on when the caddy is fully inserted.  This avoids unnecessary wear on the fan and fan noise, when the caddy is not fully inserted.  Since then I have developed two alternative and better ways of installing the microswitch referred to in that article. 

These alternatives mean that there is no need to cut one of the power wires between the fan plug and the fan.  The merit of this approach is that if the fan ever needs to be replaced, you can simply unplug the old fan, unscrew it, throw it away, screw in the new fan, and plug it in.

So here are some brief details about those ways.  The details should be read in conjunction with the earlier article.

2.  First alternative

The photos below show how the first alternative is implemented. 

Switch on power side

Switch track

Track closeup

Track soldered

3.  Second (and better) alternative

Having done one caddy that way, I took a smart pill and realised that there was an even better way to do things: 

Fan side switch

Unfortunately I am not able to include a picture of the completed soldered wiring because I have lost it and I no longer own the PC in which the cradle is now residing.  Sorry about that, but I think that you will understand what to do.