I bought an SSD and caddy to replace the optical drive in my Windows 10 laptop.  Put it all together and the SSD is not recognised - it doesn't even appear in Disk Management.  Obviously it could be a faulty caddy or SSD but does anyone have any other suggestions?

SGodfrey
I bought an SSD and caddy to replace the optical drive in my Windows 10 laptop.  Put it all together and the SSD is not recognised - it doesn't even appear in Disk Management.  Obviously it could be a faulty caddy or SSD but does anyone have any other suggestions?

The easiest way to test a SSD is to buy a cheap USB to SATA adapter cable, then plug the SSD drive into a USB port.
 
These are the cables that are usually supplied with a SSD migration kit for cloning a system HDD before SSD installation as the primary drive.
 
If that works, then determine if everything is connecting correctly via the caddy.  SATA drives need the SATA port connector + SATA power.  Make sure both are getting connected.  If your optical drive was SATA, then it should work if the SSD is good.
 
IMHO, cloning the HDD onto the external SSD, then swapping drives, using the HDD as the secondary drive would give you a better performance boost.

Without a way to test the SSD separately (from the caddy), you can't know which device is faulty.
 
Do you have a desktop you can use to test/connect the SSD?
 
Short of that, you'll need to do as abacab suggests and use an adapter of some sort.

JonD
Without a way to test the SSD separately (from the caddy), you can't know which device is faulty.
 
Do you have a desktop you can use to test/connect the SSD?
 
Short of that, you'll need to do as abacab suggests and use an adapter of some sort.

I think that the USB adapters can be had for $5 and a couple days for delivery.  But if you're in a hurry, you could pop out the HDD and insert the SSD in it's place, then power up and go into the BIOS to see if it's detected.  You could also try a test clean install of Windows onto the SSD at that point, or just boot from a bootable optical CD/DVD (Such as a Windows repair disk or Linux live disk) and test the SSD as an internal drive with some utilities.

Thanks Guys,
Lots of useful tips there.  Firstly, the idea was to avoid buying the sata usb cable by putting the ssd straight into the caddy and into the optical drive, clone the main hard drive, then swap them over.  Then I'd have the SSD as my main drive and I could reformat the old drive (now in the caddy) at my leisure.  However, enough of the cheapskate, I've bitten the bullet and mail ordered the sata cable.
I thought about the suggestion of swapping the blank ssd for the hard drive as suggested abacab, but I don't have enough confidence about using the bios and the other problem is lack of time.  I was a bit concerned about your other point that the SSD needs power as well as the port connector.  The caddy has just one connector and so does the SSD (Crucial MX300 750GB).
Thanks again for your feedback, I will await the cable and let's see what happens.

SGodfrey
Thanks Guys,
Lots of useful tips there.  Firstly, the idea was to avoid buying the sata usb cable by putting the ssd straight into the caddy and into the optical drive, clone the main hard drive, then swap them over.  Then I'd have the SSD as my main drive and I could reformat the old drive (now in the caddy) at my leisure.  However, enough of the cheapskate, I've bitten the bullet and mail ordered the sata cable.
I thought about the suggestion of swapping the blank ssd for the hard drive as suggested abacab, but I don't have enough confidence about using the bios and the other problem is lack of time.  I was a bit concerned about your other point that the SSD needs power as well as the port connector.  The caddy has just one connector and so does the SSD (Crucial MX300 750GB).
Thanks again for your feedback, I will await the cable and let's see what happens.

My description of the SATA SSD connectors was based on placing a SSD in my tower PC case using the conventional separate data and power cables, rather than a caddy.
 
The optical drive bay caddy should present the necessary SATA connector pins for data and power to the SATA drive.
 
When I bought an external USB enclosure for a SATA 3.5" HDD, the internal connector (probably similar to your caddy) was a unified type bracket that had pins for the data and power connectors on the drive to plug into. Check that these are attached securely.  Try re-seating the drive.
 
It's also possible that something isn't making contact in this arrangement, so some process of elimination becomes necessary.  After you finish cloning the HDD and swapping the drives, you can try the HDD in the caddy .  That should tell you if the caddy is functional.  You already know the HDD is good

As I was putting the caddy away for the time being, I noticed a tiny 3-way micro-switch beside the sata socket.  There's no documentation, any idea what it might be?  I wonder if it's related to power supply?

No idea.  Time to hit the web.  If the manufacturer site is no help, Tom's Hardware Forum is one place for builders to ask questions ...
 
http://www.tomshardware.com/forum/
 
For example, I tried this search term there [laptop drive caddy], and got this list of results:
http://www.tomshardware.com/s/laptop+drive+caddy/

There are other threads on this, but having done it myself recently, I have a tip which may be of use if you are cloning the main drive to make your new SSD the main drive.
After cloning successfully, turn off the pc, connect the SSD into the SATA port your original main drive was in leaving the old main drive disconnected.
Boot up and hopefully it should boot to the SSD. If not check the boot order in your bios.
Once you have booted successfully once, your should be able to shut down, reconnect your old main drive into another SATA port and reboot. It should boot from the SSD and you should be able to see your old main drive and reformat it if you want.

Hatstand
There are other threads on this, but having done it myself recently, I have a tip which may be of use if you are cloning the main drive to make your new SSD the main drive.
After cloning successfully, turn off the pc, connect the SSD into the SATA port your original main drive was in leaving the old main drive disconnected.
Boot up and hopefully it should boot to the SSD. If not check the boot order in your bios.
Once you have booted successfully once, your should be able to shut down, reconnect your old main drive into another SATA port and reboot. It should boot from the SSD and you should be able to see your old main drive and reformat it if you want.

Hi Hats
That was my exact plan, obviously great minds think alike!