The Lapkow machine

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Re: The Lapkow machine

Postby Steve Anderson » Tue Nov 08, 2016 9:04 pm

Viewmaster wrote:I tried connecting the 3v laser to the USB supply with a series resistor but no success so far.

There is a limit of 100mA on a USB port so if your laser uses more than that the port shuts down. If it's an active USB device during initial handshaking it can request up to 500mA should it need it. But I would be surprised if a laser diode needed anything like that much. If the PC is a laptop the limits could be lower, but they shouldn't be. Try an ordinary (visible) LED at 10mA first. Yer average red LED in series with 330R should do it.

Steve A.
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Re: The Lapkow machine

Postby Viewmaster » Wed Nov 09, 2016 12:17 am

Thanks for that Steve.

I don't know what went wrong. Maybe as I am running ADC/buffer/2 off volts comparators/video amp etc all
from USB, it closed down, although all these devices take very, very much less than 500m/a.

I checked current the laser took when run on 3v batteries and it was only 25m/a or so.

Anyway, on trying again all seems to be OK now. My Lapkow trial set boards are one great big mess
at present so maybe I had a short somewhere. :(

I would like to run everything, (except 2 motors) , from the USB as the running laptop
gives me 5v for free. :)
“One small step for a man,"......because he has Arthritis.
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Re: The Lapkow machine

Postby Viewmaster » Wed Nov 16, 2016 7:19 pm

Well everything should now work but it ain't! :)

I have both line and frame, start and end pulses, available from the scanner but
cannot get 'em to work in the program.

I now plan to slow everything down in order to carefully study if the sequence
of everything is correct and is constant.
Something is running out of kelter somewhere methinks.
“One small step for a man,"......because he has Arthritis.
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Re: The Lapkow machine

Postby gary » Wed Nov 16, 2016 7:34 pm

Viewmaster wrote:Something is running out of kelter somewhere methinks.


It always does :-( but that's half the fun! :-)
Perfecting an NBTV system is like trying to slam a revolving door...
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Re: The Lapkow machine

Postby Harry Dalek » Thu Nov 17, 2016 2:04 pm

Good Luck Albert fingers crossed i know some times they work some times not ...but if theres a will theres a way .

Some times you can work on it non stop and never get any where ....the Slow scan mechanical television i put it away for a year i think ...took it out for another try and with in a day it was Cooperating...
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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