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mirror of git://projects.qi-hardware.com/wernermisc.git synced 2024-12-24 05:33:20 +02:00
wernermisc/labsw
2011-09-18 00:49:38 -03:00
..
components labsw/: grouped opto-couplers for socketing; improved clearance of inputs 2011-08-28 10:46:02 -03:00
draft labsw/: moved base and front Xfig drawings to draft/ 2011-09-01 10:16:48 -03:00
fw labsw/fw/labsw.c: improved debouncing and cleaned up button logic 2011-09-11 13:03:20 -03:00
mech labsw/mech/front.fpd: reduced width from 104 to 103.6 mm, LED hole from 6.9 to 6.2 mm 2011-09-05 14:09:13 -03:00
modules labsw/: removed copper from mounting holes 2011-09-12 14:30:19 -03:00
pcb labsw/pcb/Makefile: increased clearance from 2 mm to 3 mm 2011-09-01 12:04:02 -03:00
tool labsw/tool/: basic labsw control utility 2011-09-06 04:21:36 -03:00
web labsw/web/: added visual indication of test loop 2011-09-12 08:27:36 -03:00
back.sch labsw/ changed internal pull-ups to external to remove sneak current path 2011-09-10 20:23:59 -03:00
BOOKSHELF labsw/BOOKSHELF: added the BAS16WT flyback diode 2011-09-05 15:34:16 -03:00
ch12.sch labsw/ changed internal pull-ups to external to remove sneak current path 2011-09-10 20:23:59 -03:00
front.sch labsw/: added low-pass filters to button input (with help from Joerg Reisenweber) 2011-09-10 20:35:23 -03:00
labsw.brd labsw/: made column cavities 0.2 mm wider on each side 2011-09-18 00:49:38 -03:00
labsw.cmp labsw/: added hardware revision indication 2011-09-10 20:42:00 -03:00
labsw.pro labsw/: reduced depth of "bays" for columns from 11 mm to 10.4 mm 2011-09-01 04:42:41 -03:00
labsw.sch labsw/: added hardware revision indication 2011-09-10 20:42:00 -03:00
LOG labsw/: made column cavities 0.2 mm wider on each side 2011-09-18 00:49:38 -03:00
Makefile labsw/: BOOKSHELF and mechanical drawings 2011-08-23 11:51:39 -03:00
README labsw/README: all opto headers need wider spacing for high voltage 2011-09-11 13:13:18 -03:00

Opto-isolated inputs
--------------------

The C8051F320 needs a current of at least 50 uA to drive an input low.
The current transfer ratio of the opto coupler is 50% or better.
Thus we need an input current of at least 100 uA.

If we allow for a loss of at least 100 mV (yielding a minimum input
voltage of 1.5 V), the protection resistor can be at most 1 kOhm.

If the maximum power dissipation of the protection resistor is
limited to 1 W, we can allow up to 30 mA into 1 kOhm +/- 10%.

The maximum input voltage would thus be 30 V.


Future changes for higher voltages
----------------------------------

The circuit is currently not designed for voltages exceeding about
30 V between any two points !

To allow the use with mains voltages, be it across the relays or be
it as a difference in "ground" potential of separate loops, at least
the following changes will be necessary:

- air gaps must be 2 mm or larger (6 kV)
- conducting elements closer than 2 mm must be isolated if high
  voltage may exist between them

In particular, this means:

- the PCB must be coated
- opto couplers may not share the same socket
- the opto coupler headers (inputs and outputs) need wider spacing
- clearances need to be verified