12vDC to 9vDC

[wkel50]

I have a Metz flash gun that can use Quantum battery pack rated at (QB2R) 9 volt, 3.0 amp-hours and I have been given a battery pack rated (QB5) 12 volt, 2.1 amp-hour. Now, I need an in line converter to drop down to 9vDC, any ideas please. ie. would this item from ebay work 170231695239
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... :IT&ih=007. Thanks.

[Simon (Webmaster)]

Hi

Yes, that should work. Obviously you will either need a suitable socket on the battery pack to connect it to (try www.maplin.co.uk) or dismantle the adapter and simply use the cirtcuitry inside.

If you want a more 'technical' solution use an 7809 voltage regulator (Maplin code UJ55K) along with the necessary decoupling capacitors as shown in the application notes in the datasheet - see http://www.datasheetcatalog.com/datashe ... 09CV.shtml. However I suspect you are after a ready-made solution, in wich case the ebay adapter is probably your best bet.

[wkel50]

Thanks Simon, I was looking for a ready made solution, but having seen the application notes and having made up simple projects in the past, it seems there are only three components? and simple board? or is it that simple.

[Simon (Webmaster)]

The normal circuit (without looking at the app note) is the regulator with a ceramic capacitor on the input and output (often 0.1uF) to prevent it oscillating. It's a good idea to put an electrolytic capacitor on the input too - say 220uF 16V, but not absolutely necessary with a battery supply. The voltage regulator might need a heatsink, although for your application you might get way without it. If it seems to run warm in use add a small heatsink or fashion one out of a bit of tin (e.g. baked beans can ). You could build the whole lot on stripboard - remembering to leave space around the voltage regulator for the heatsink to fit if it turns out to be needed.