Truncated match.
PICList
Thread
'Optical encoders and Telescope Control'
1998\01\28@083745
by
Keith Howell
Philip Cowley wrote:
> If I put the 2016s right by the encoders
> then I have a long parallel cable...
> But if I put them next to the PC then I have long leads
> carrying the quadrature signals... Very noisy.... Any ideas???
The quadrature signal wires sound the lesser problem.
Suggestion in order of convenience:
- Twisted pairs
- Co-ax
- Buffer to RS485 levels (0-5V complementary)
- Buffer to fibre-optics
The last point made me think: encoders sense the interruption
of light beams. Why not pipe these beams down fibre-optic cables
to photo-transistors, Schmitt triggers, HCTL 2016 chips etc
near the PC?
Shotgun-section fibre-optic cable would carry two signals
from one encoder. You still have to power the LEDs,
but as these are near motors this should not be a big deal.
Keith.
1998\01\28@094324
by
Walter Banks
> Philip Cowley wrote:
>
> > If I put the 2016s right by the encoders
> > then I have a long parallel cable...
> > But if I put them next to the PC then I have long leads
> > carrying the quadrature signals... Very noisy.... Any ideas???
Put a micro near the encoders and use one of the differrential
serial links like rs485. It is good for a considerable distance,
uses serial ports and is quite reliable.
Walter Banks
1998\01\28@101553
by
Philip Cowley
>> The only problem I can see is the distance from the encoders to the PC...
>> about 30 feet!!! If I put the 2016s right by the encoders then I hav a
long
>> parallel cable... Not good! But if I put the 2016s next to the PC then I
>> have long leads carrying the quadrature signals... Very noisy.... Any
>> ideas???
>
>Put the 2016s by the encoders, put a PIC by the 2016s and use rs232 to
>the PC.
What I think I'll do is...
Encoder -> Schmidt Trigger-> Line Driver -> twisted pair cable ->
Receiver -> HCTL2016 -> I/O Card -> PC
The schmidt trigger gives me a nice waveform for the signals. The line
driver shifts the voltage up to +/- 12V and transmits it over twisted pair
lines. The receiver brings the voltage back down to 0-5V. The I/O card
drives the 2016 directly. I already have the I/O card and it works a treat!
Phil
'Optical encoders and Telescope Control'
1998\04\05@120112
by
Keith Howell
Hi PC.
Just a follow up note to see how the scope automation is going.
More... (looser matching)
- Last day of these posts
- In 1998
, 1999 only
- Today
- New search...