The Super Miniar™ 20mA - 100mA Driver

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Some basic design goals of the project:

• Drives case neutral and isolated diodes
• Ultra low dropout, <400mV
• 20mA - 100mA Operation with zero overshoot
• 2 - 10V Operation
• Potentiometer adjustable
• Bottom side free of components for optimal heatsinking
• Driver fits inside an AixiZ module - 9 x 15.73mm
• TTL Input - Still testing
• Simple design using only 5 components

All of the above goals have been met or
exceeded, aside from the TTL input testing.

Let's have a look at some waveforms.

Startup @ 20mA



Shutdown @ 20mA



Startup @ 100mA



Shutdown @ 100mA



Drift - there is none. This was really
surprising. The output current never seems
to drift more than about 100µA once it
reaches steady state. I had expected some
drift, especially in the higher ranges. I
don't think I've seen anything like it. It
wasn't me, I swear.

Varying the input voltage and number of
diodes in the test load does not change the
output current. Not even 1mA

Rev. 2 boards will be completely free of
wirepads to make heatsinking even easier.
At 100mA a heatsink is unneeded, though.
Maybe only if there is a lot of voltage to
drop.



So I have one Rev. 1 board for sale right
now for someone who wants to try these
out. The Rev. 1 boards do more than
100mA. Just how much more is a surprise!
(That requires a heatsink) They are also a
little longer, but still fit inside an AixiZ
module. More will be on the way when
the stencils arrive.
:thanks:

Fantastic project. +1 !

What model scope do you have, and do you recommend it?

:thanks: It's a Rigol DS1102E. There are
some better ones out now, but it's an okay
scope for driver testing. My main gripe
with it is the PSU noise spikes in the low
ranges, but it is possible to get clean
captures. It just takes a little effort.

Three months later... (sorry)

Do you have some of these drivers? I want to replicate your 685 pen build. I've also never built a laser before so I'm deep in the woods here. Any help would be appreciated.

Thanks,
-cutyall

cutyall said:

Three months later... (sorry)

Do you have some of these drivers? I want to replicate your 685 pen build. I've also never built a laser before so I'm deep in the woods here. Any help would be appreciated.

Thanks,
-cutyall

Click to expand...

It's not complicated. Just think of a normal build, with about a tenth of the space

I'm currently busy with another project right
now, but can build a few for you in a couple
weeks or so.