Tube Time Delay Relays

[Tom Bavis]

Believe it or not... Amperite delay tubes are still in production and you can find a data sheet here: http://www.amperite.com/Uploads/g.PDF

Contact rating is 120V, so you need to use a relay to switch the B+ (Potter & Brumfield T92 has a 400V rating...). I recall that their data sheet USED to recommend using a latching relay with these tubes which removed heater power once they close for two reasons - it saves heater life and will be able to delay again immediately after a short shutdown (since it has cooled down).

[erichayes]

Hi All,

Amperite's specification code was: first digit(s) = heater voltage; NO/C = cold status of contacts; second digit(s) = delay time in seconds. Thus, a 6NO20 would have a 6 volt heater, normally open contacts and a 20 second delay. I believe the letter suffix denoted what kind of bottle (9 pin miniature or octal) was used.

A latching relay can be made using a DPDT relay. Use one set of contacts to control the B+, and the other to supply the delay relay heater in the normally closed position, and the relay coil in the normally open (energized) position. There's enough thermal inertia in the delay relay that the power relay will latch even though heater power is removed from the delay. Obviously, the heater of the delay relay must be the same voltage as the coil of the power relay.

Connect one of the delay contacts and one side of the heater together, and connect this junction to the normally closed contact of the power relay. Connect one side of the power relay coil to its normally open contact, and connect this junction to the remaining delay relay contact. Connect the remaining coil and heater leads together, and connect this junction to one side of the power source (6 volt, 120 volt, whatever) and the remaining (armature) contact of the power relay to the other side of the source.