On 11/28/2014 8:41 PM, Brent Hilpert wrote:
I do have a design that sounds like what you want
using 3 standard relays: one D/3PDT & two 4PDT (or, one D/3PDT, one 3PDT, one 4PDT),
or probably best to just call it three 4PDT relays.
A single NO pushbutton would control the relays, wired to produce a net divide-by-2
effect.
Contacts on one of the relays would be used for the ON/OFF, in series with DT contacts on
one of the others to direct the UP/DOWN.
It's actually on-topic, as it's from a design exercise I did for the Simon relay
computer.
The (whole) schematic is linked on this page:
http://www.cs.ubc.ca/~hilpert/e/simon/imp.html
See the top-left corner of page 2 of the schematic, the ?, ?a & ?b relays.
There's a timing diagram in the timing section on the web page, the ? signal would
correspond to the button pushes.
It might be possible to reduce the number of contacts if one stared at the circuit long
enough.
I looked at it for a while, and laid it out in Eagle, and I see what is
going on. Thanks for the idea.
I tried to simplify, but aside from using a few diodes to reduce the
number of poles in the Phi relay, I see no way to get around needing 1
4PDT (Relay A) and 1 3PDT (Relay B). Still, it's a plan.
Perhaps the solenoid-triggerred 'mechanical
flip-flop' relay Brian pointed to is closer to what you want. One thing to note about
that type is when the system is turned off it can be left in - and hence will power-up in
- either of the two states, you wouldn't know initially whether it was going to go up
or down, unless you knew from the last time it was operated.
Yes, I like your idea, because it always starts from a known state. But,
at least I have two options. I'll buy some 12VDC relays this week to
wire it up.
Jim
--
Jim Brain
brain at
jbrain.com
www.jbrain.com