DIY Bench Power Supply #2 - Initial Circuit draft and parts

[exekutive]

Hi Martin. In video #1, you mentioned using a stencil to do the lettering on your college power supply. Can you perhaps show an image of kind of stencil you used? The result looks pretty good.  Thanks.

[Paul Collins M0BSW]

I can speak from experience, you can without thinking stick one into one of your  fingers,and yes it hurts a lot for several day's  and I can also speak from experience that you can add at least 20 New swear words to your repertoire,

[MJLorton]

I've not seen those transfer stencils for years. I did a quick search online and could not find any. It used to come in the form of an a4 sheet or other sizes with a whole host different of fonts. You then held it against the surface you were "printing" on and rubbed over the top of the sheet with a pencil that transferred and stuck the lettering onto the surface.

Perhaps ask an art supply store?

[SeanB]

Does look like Letraset no longer supplies them, though they still have the crepe tape in assorted widths for use as traces. They still do lettering in assorted fonts and some graphics, but it looks like the PCB layout stuff has disappeared. Not surprising as they were IIRC quite expensive per sheet, and a sheet did last for a long time.

Only thing is that you had to be aware of scale, as the sheets were IIRC available in either 0.1 or 0.15in spacing, and in either full size, 2x or 4x enlargements for photographic reduction onto acetate film to master the board, or to be used with a photographic exposure unit to directly expose the sensitised PCB sheet. I had a lot of fun with that, though I did find out the hard way ferric chloride will stain almost everything.

[Paul Collins M0BSW]

Letraset: still available in the UK,WH Smith do their version, not forgetting E-Bay of course.

[exekutive]

How To Use Dry Transfer Lettering
https://www.youtube.com/watch?v=ed6iXQW_O1U

9.5mm Rub-On Black Letter Transfers, 'Letraset type' for Art & Craft, BL74
http://www.ebay.com/itm/181529946619
Mecanorma Dry Transfer Lettering Sheet A3, Rub-on, Letraset #65
http://www.ebay.com/itm/381090589041

http://www.archertransfers.com/AR35108B.html

[phil]

I built the DIY Bench Power Supply and it seems like the constant current will not go below about 30 MA. It would be nice to go down to 10 MA or so, to test LED's, and etc.
Anyone have any mods to lower the constant current?

[MJLorton]

Hi Phil, I also saw a problem like that on my test circuit. Try a diode on the emitter of the 2n222 transistor (ouput of the current sense op amp ) to the negative rail. I've not tried this yet but post if it works.

Cheers, Martin.