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encoder based line triggering

I am looking to trigger a linescan camera off of an absolute/linear encoder position of a stage with .1um encoder. My problem is that I need to trigger at around 9kHz, and my servoloop is only at 4kHz, so I can't run the trigger off of the motion controller's position capture.

I guess what I want to do is multiply the encoder pulse train by say

10X, and then have a variable divider circuit that would allow me to say pulse every .5um(50 counts after 10X) at one velocity, and at .25um(25counts after 10X) at another, and so on. It has been a long time since I've done board level stuff, as I took the route of system level design in my career, and I am not ashamed to ask for help. All I have been finding IC wise are high frequency stuff, which I'm not sure would be ok with such low frequency signals.

Thanks in advance for any advice or help you can give me,

Brian

Reply to
brian.blut
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The part you want is probably the CD4046 or one of its many variants,

The Philips 74HCT9046 is a nice part, and DigiKey stocks it.

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Read the application note carefully, and make sure that you end up with a critically damped phase control loop.

The 4046 oscillator will run at speeds up to about 10MHz, which should cover your application.

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Bill Sloman, Nijmegen
Reply to
bill.sloman

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Thanks Bill, but a PLL will not work for my application, as I can't have it guessing when the next encoder pulse will come. I think I can use a higher res encoder to get the multiplication that I need. Would I want to use a simple counter/timer to accomplish this then? The resolution I am proving this at is triggering every 5 encoder pulses even with my current encoder. So... what I want to do is wait until the rising edge of the fifth pulse, and then fire off one ttl output.

Thanks for your help,

Brian

Reply to
bblut

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Which wipes out any system for multiplying an encoder output. In fact mechanical systms with interia have relatively low high frequency noise, so a properly tuned PLL might work, but a higher resolution encoder is obviously a much better idea.

That is what counters do. Use a synchronous counter rather than a ripple counter.

The 74HCT40103 programmable 8-bit counter would be well worth looking at - it is specifically intended to do your job.

If you wnat to get fancy, you can always program an in-system-programmable programmable logic device to produce your programmable counter and your glue logic. The Xilinx CoolRunner chips are fast and not all that current hungry.

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Bill Sloman, Nijmegen
Reply to
bill.sloman

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