Thread: Speed of Optos on BoBs
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24-08-2012 #21
Personally, unless its causing you problems I'd leave it alone.... if you need more speed you might want to consider a different card. When you say a 3.5v swing, between what and what? 3.5v is a good logic one level...
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25-08-2012 #22
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25-08-2012 #23
Ah, so the transistor is not saturating. with 100R load, the collector current therefore is (5 - 1.6)/100 = 34mA, whereas it needs to be (5-0.5)/100 = 45mA, so the LED needs to be driven harder as previously discussed. However the 74HC14 clamps at 20mA, so there may be a limiting factor here... try reducing R1 from 1k to around 450R or so, theres no point in going lower... if that doesnt improve things then its not going to get better without significant rework
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25-08-2012 #24
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03-09-2012 #25
A week on and spare time now permits the process of clean-up the O/Ps with a few 74HC14s, It ain't gonna be petty but at least the waveforms, both inbound and outbound, are gonna be sharp. With a bit of care I will retain the complete opto-isolation on the BoB. Elimination of the now un-necessary optos at the front end of the single axis TB6560 will follow blow by blow.
I think it's fair to say "although any CNC electronics system is a series of steps it needs to be integrated as whole to get the performance expected"
The overall plan continues to be to derive the PC side supply from a spare HDD power connector within the PC. The O/P side of the BoB will come from the 5v rail of the homebrew smorgasbord driver PSU. Or have I got it totally wrong?
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