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l_gaminde
- 21st April 2011, 19:44
Im just starting my thinking! I need some ideas on reading a variable string of pulses (FREQ) and outputing a different string of pulses maybe devide by 2 to start. this is for a dc 4hp motor with speed sensor I want the controller to think its not up to speed and ramp up higher. could use either hardware or software maybe ideas on both for testing.
rmteo
- 21st April 2011, 20:16
To divide a pulse train by 2, you don't even need to use a PIC. There are many discrete devices that will do it. My favorite for these sort of applications is the 74HC390. It can be used to to implement various combinations of ÷ 2 up to a ÷ 100 counter at up to 50MHz and operates from 2.0 to 6.0V. It comes in a variety of packages including DIP16 and cost <$1.
l_gaminde
- 21st April 2011, 23:30
will i be able to change the duty cycle or will it just give a quick pulse, not sure what I really need at this time. I have plenty of 84s 628s and others. I would have to order the 390 part. I did consider this option already had the digital Ic gallery book out. Im thinking pic to start. once i get it working (see if it will work) then move on but price is about the same.
l_gaminde
- 28th April 2011, 03:16
Rmteo

I got a couple of the 390's have it sort of working, it seems to be pulsing. Am I correct that I must hit the clear pin every cycle as I could not get it working without this the circuit diagrams do not show this. What I did is take the output of q0 to the clock of ck1 and the output of I think q3 or q4 to the clear pin does this sound correct I tried to clear every pulsout of q0 but got nothing.

thanks larry
rmteo
- 28th April 2011, 04:19
Not sure what you mean by the clear pin. There is an MR (Master Reset) pin that when held high forces all outputs low. To divide by 2, connect the Q0 output to the CP1 input. Apply your signal to CP0 and Q0 will give you a /2 output (ensure that MR is held low).
l_gaminde
- 28th April 2011, 23:58
rmeto

Thanks for your help, I tried grounding the MR pin and got nothing when I first started, after reading your last post I wired it low and it worked great this is much better setup.

now as far as 32 bits being better not sure I agree
my brain is only 2 bits so it seems a Waste!!