16 Output Servo Board
Hello,
1. Does anybody know the frequency of the pulses that come out of the 16 output·servo board?
2. Can the frequency of the pulses be changed?
3. Has anyone used this board·with a pc and·Visual Basic?
4. Is it hard to program Visual Basic to use this board?
Thanks,
DigitalDj
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1. Does anybody know the frequency of the pulses that come out of the 16 output·servo board?
2. Can the frequency of the pulses be changed?
3. Has anyone used this board·with a pc and·Visual Basic?
4. Is it hard to program Visual Basic to use this board?
Thanks,
DigitalDj
·
Comments
so when you ask if the "frequency of the pulses" can be changed -- well first, you HAVE to change the width of the high portion, and second, what other frequency would you want to change?
OK, I assume you mean this: http://www.parallax.com/detail.asp?product_id=28023
Which is the "Parallax Servo Controller" or PSC. Since its input is serial based, you SHOULD be able to use it with VB, if you know any serial port programming. You will need a MAX232 to convert the PC's +- 10 volt RS-232 levels to the unit's 0 to 5 Volt levels -- adapters are available.
rounder
http://forums.parallax.com/showthread.php?p=527763
·PS Ignore the first post in that thread and concentrate on the second post with corrected and cleaned up code.
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Is it supposed to smoke like that?
Post Edited (rounder) : 3/11/2005 5:00:16 PM GMT
What i want to find out if i can use this board to control some l.e.d. light since the board uses Pulse Width Modulation. I just need to know if it can be used that way. I know most pwm circuits use over 1khz frequency for the pwm. I want to use rgb l.e.d's and do color mixing.
Thanks,
Kevin
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Jon Williams
Applications Engineer, Parallax
Dallas, TX· USA
What is the difference between the SX28ac/dp pwm and the servo board pwm? I had a gentleman from Parallax that told me that i could use the servo board just for the pwm and control l.e.d's! I don't have to change the pulse width but i thought it would be nice that way i could compensate for color inconsistencies. I was using the PakV(SX28AC/DP) from AL Williams but was having problems with the address pins for multiple chip operation and one of the pins was blowing the chip. The PakV(SX28AC/DP) chip does proportional mode approximately 2uS time slice) or equal area PWM (duty cycle of a 512uS period).
Thanks,
Kevin
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I had tried to respond earlier but I was unable to find the thread using keyword search until I remebered Jon wrote it, then it was an easy find using Posted By searching.
For full range control of LEDs you want 0-100 percent duty cycle PWM, the servo board having·the dedicated function of operating servos has limited functionality, I would venture to guess trying to use the servo board will give you a range of extremely dim to dim since its pulse duty range is between 2.5-12.5%
One last thing, if you decide to design your own pwm chip using the SX28 you can get all 16 channels of PWM on the same chip with 4 pins left over for other interfacing needs.
Post Edited (Paul Baker) : 3/11/2005 10:49:47 PM GMT
You may have been told that you could use the PWMPAL for servo and/or other control because you can change the entire cycle -- on the PSC the only that that can be changed is the high-going portion of the cycle (low is fixed at 20 ms), and the high-side pulse has a limited range.
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Jon Williams
Applications Engineer, Parallax
Dallas, TX· USA
1. What will the difference do to the l.e.d's using the servo board pwm as compared to using the SX chip pwm? 2. Let's just say i want to do nothing more but control the brightness for now, will the servo board do the trick?
3. Will the new servo board that will have usb connection be setup the same way?
Thanks,
Kevin
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A Servo board is for driving servo's, which have the signal requirements mentioned above. This stuff is not magic, you know, things have interfaces, and boards are engineered to support those interfaces. If you want to get creative, then things may or may not work. In this case, the PSC board will only drive LED's to 10% brightness. The new USB board will do that over a USB port -- still not what you want.
You do need the PWMPAL, which CAN drive LED's to 100% brightness.
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