Relay computers

From: Dwight K. Elvey <dwight.elvey_at_amd.com>
Date: Fri Sep 24 15:45:08 2004

>From: "Tom Jennings" <tomj_at_wps.com>
>
>On Fri, 2004-09-24 at 07:39, Ade Vickers wrote:
>
>> If each relay needs, say, 25mA _at_ 6v to operate, then the peak current
>> draw
>> of our R80 (as I shall call it) could be around 600A (I think). And
>> that's
>> before we've added memory, i/o, etc.
>
>Last things first :-) the place to look for this is telco. They did
>really for real. Most of them are 48V; it lowers current plus higher
>voltages help with the inductive time constant thing (take a look at how
>teletype loops are done; HV, a series resistor shortens the *effective*
>time constant (eg. the time to reach 60mA in the tty case).
>
>

Hi
 Increasing the resistance doesn't change the power needed
to pull in the armature, all it does is decrease the time
constant for a particular inductance. Higher voltages require
more resistance in the wire, meaning more turns. The pulling
effect on the armature is just ampere-turns. Using more resistance
just means higher voltage. E^2.
 One can do the same thing by adding a resistor in series with
the 6V coil and using a higher drive voltage. Power wise, it is
a loss. You still need the effective 25mA in the coil.
Dwight

Dwight
Received on Fri Sep 24 2004 - 15:45:08 BST