Hi all , I m working on a parallel port breakout board for CNC controller which will send step/direction pulses to stepper driver.
The controller software(Mach3) will generate pulses @ 25Khz , 35Khz , 45Khz , ... as per my setting. Personally I think 25Khz is enough for me and I probably wont go over 45Khz ever. Also the pulse width of these pulse is between 3us(min) to 15us(min) which can be set by user.
After googling around I found some optocoupler ICs like PC817/PC827 , CNY117 , Ltv847 , 6N139 , H11L1M.
Ltv847 , 6N139 , H11L1M seem to be fast. H11L1M has in-built schimmt trigger while the other 2 don't .. so H11L1M seems to be the candidate but its costly as compared to LTV847 , PC847.
I would like to know about better &/or cheaper alternatives for the above ICs considering my design requirements.
At the moment I am stuck between LTV847 and PC847.
I found some design guidelines in C11 parallel breakout board manual @ http://www.kelinginc.net/C11Manual.pdf
As shown in Fig 1 ,2 (attached) they have used buffers before and after optocoupler. I guess they have used buffers on output because of low current transfer ratio(CTR) which might not be able to drive the LEDs .. am I correct ? Can some one please explain the use of buffer before optocoupler ?
I need help in determining correct values for R and C in Low pass the filter.
The controller software(Mach3) will generate pulses @ 25Khz , 35Khz , 45Khz , ... as per my setting. Personally I think 25Khz is enough for me and I probably wont go over 45Khz ever. Also the pulse width of these pulse is between 3us(min) to 15us(min) which can be set by user.
After googling around I found some optocoupler ICs like PC817/PC827 , CNY117 , Ltv847 , 6N139 , H11L1M.
Ltv847 , 6N139 , H11L1M seem to be fast. H11L1M has in-built schimmt trigger while the other 2 don't .. so H11L1M seems to be the candidate but its costly as compared to LTV847 , PC847.
I would like to know about better &/or cheaper alternatives for the above ICs considering my design requirements.
At the moment I am stuck between LTV847 and PC847.
I found some design guidelines in C11 parallel breakout board manual @ http://www.kelinginc.net/C11Manual.pdf
As shown in Fig 1 ,2 (attached) they have used buffers before and after optocoupler. I guess they have used buffers on output because of low current transfer ratio(CTR) which might not be able to drive the LEDs .. am I correct ? Can some one please explain the use of buffer before optocoupler ?
I need help in determining correct values for R and C in Low pass the filter.
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