Wesley Moore wrote: > I'm trying to answer a couple of general questions that don't seem like an > easy find on the wiki, etc. Yes I know there are many contributing factors > involved on accurate answers, so a rough ballpark is all I'm looking for. > > Without additional hardware: > How many encoder counts per second can be handled? > Up to 1/2 the frequency of your base_thread is absolutely safe. Approaching the base_thread frequency should be OK, but you need to leave headroom for errors in the encoder and timing jitter on the computer. You don't want to risk overrunning the encoder counter or it will miss counts. > What is the PWM frequency range available? > > PWM frequency is limited by resolution. If the Base thread is running at 20 KHz, then a 10 KHz square wave can be generated, or a 5 KHz PWM wave with 0, 25, 50, 75 or 100% duty cycle. If you want greater resolution of the duty cycle, you have to reduce the PWM frequency. > Same questions with additional hardware (Mesa, etc) and the estimated add-on > cost? > > The Pico Systems PWM controller has a 40 MHz clock for the PWM generator, so it adjusts PWM output in 25 ns steps. At 50 KHz, it has a resolution of one part in 800. It can count encoder pulses approaching 1, 2.5, 5 or 10 MHz. (I say approaching, as there is almost no sampling time jitter, but you still need to leave a margin for timing variations from the encoder.) (For those familiar with this product, yes, this is a new feature, switch-selectable encoder filter rate.) The 4-axis PWM controller is $250, and includes the encoder counters, PWM generators, 15 opto-isolated digital inputs, positions for 8 solid state relays of your choice, and and an E-stop circuit. An additional board can be added to the same parallel port to handle 4 more axes. A $50 DAC can be added to control the spindle speed, laser power or whatever.
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