Hi Chris,
I've added the encoder part number to the schmeatic and also added
datasheets and 'Halscope' screen shot to the webpage:
https://www.purbrookengineering.com/index.php?option=com_content&view=article&id=11
I don't have an oscilliscope so am relying on Halscope at the moment.
Thanks,
Pete
On 11/10/2021 02:58, Chris Albertson wrote:
sorry there was no part number on the encoder. I figured it was the generic
Omron clone that is 5 to 12 volts. But there are two kinds that other is
12 to 24. volts. See in the link below
https://www.ia.omron.com/products/family/486/specification.html
Is the encoder "open collector" or voltage output. If open colector pull
the outputs up to 5 volts.
Placing an encoder part number of the schematic would help.
Can you post a picture of "ghost pulses", if using an analog scope just use
you phone camera, most digitalscopes can save the scree to USB drive.
Noise like this is best eliminated at the source
On Sun, Oct 10, 2021 at 1:04 PM Peter Hodgson <peterjohnhodg...@gmail.com>
wrote:
Hi Chris,
The encoder datasheet gives a voltage range of 10-30vdc so I don’t think
direct connection with 5vdc would be an option.
Would a direct connection via voltage dividers eliminate the ‘ghost
pulses’ being picked up by the Pico board?
The encoder won’t be running above 3,000 rpm.
Pete
On 10 Oct 2021, at 19:00, Chris Albertson <albertson.ch...@gmail.com>
wrote:
Is your math right? Yes, I get 83 KHz for a 500 line encoder at 10,000
RPM. Yes that is < 1% of the isolator's rated speed (of 10 MHz)
But the schematic had an RC low pass filter in the encoder output that
would have prevented the system from working above about 1000 RPM. I see
this is gone now.
But why are these isolators even needed? Why not simply operate the
encoder at 5 volts?
Or if you must run the encoder at 12 volts, you can do level translation
with a resistor voltage divider.
There is nothing yo isolate. The entire system runs on a common ground
and
there is no high power devices in the schematic and I assume the entire
system is in one building with no long (100 meter) cables
If you are worried about accidents blowing up the controller, use diodes
to
shunt any transients. But really there are no inductive loads
On Sun, Oct 10, 2021 at 10:25 AM John Dammeyer <jo...@autoartisans.com>
wrote:
From: Gene Heskett [mailto:ghesk...@shentel.net]
If the opto's are fast enough, you should be
fixed. A 500 ppr encoder s/b fine. A 1024 or 1000 requires a faster
opto.
HI Gene,
Comparing the cheap far east BoB optos with the HCPL2621 is apples and
oranges.
A 2500 line encoder still only creates 2500 pulses. The quadrature just
looks at two lines and 2 edges for 10,000 edges. But the max speed of
his
encoder is 10,000 RPM which in RPS is 166.7 and would result in 417kHz
which is 4% of the opto max 10 Mbps capabilities if the encoder was
2500
line.
But his is 500 line so at 166.7 RPS is 83kHz which is 0.8% of opto
capabilities.
John
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Chris Albertson
Redondo Beach, California
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