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I'm new to relays and still learning terminology. "Make before break" and "break before make" both make sense to me.

Is there such a thing, or a specific term for "break before make" relay that can delay between breaking and making connection?

I'm attempting to trigger a projector screen up/down signal using a relay, but it seems to be switching too fast. If I manually connect the wires, things seem to work (i.e. connect COMMON + DOWN, disconnect, connect COMMON + UP)

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  • \$\begingroup\$ You can use one relay to trigger a time-delay relay... \$\endgroup\$
    – Ron Beyer
    Sep 11, 2019 at 18:28
  • \$\begingroup\$ Not aware of a specific relay that would combine these features. I think you would need to use the output of one relay to control a time delay relay. Both could share the same supply and load. \$\endgroup\$
    – Robert Fay
    Sep 11, 2019 at 18:36
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    \$\begingroup\$ I believe that 2 individual relays are typically used for this kind of task. \$\endgroup\$
    – brhans
    Sep 11, 2019 at 18:37
  • \$\begingroup\$ Thanks for the feedback! Combining multiple relays makes sense. \$\endgroup\$
    – russdot
    Sep 11, 2019 at 18:40
  • \$\begingroup\$ @russdot -- any reason you can't use a single timing relay? Like a DIN style general-purpose timing relay? \$\endgroup\$
    – user199402
    Sep 11, 2019 at 18:42

3 Answers 3

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If you need a delay between break and make that is anything more than in the millisecond range then your best bet is to use two separate relays for this application. You can integrate a simple electronic control circuit between the input control signal and the two relay coils to take care of the delay characteristics that you would need. The following simple circuit implements a break-delay-make for both transitions of the input control signal.

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You would wire to the individual relay contacts to achieve the type of switching that you need for your application.

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There are time delay relays. Most relays are break before make by the nature of the contact structure. search "time delay relay", then ask the application folks from whatever manufacturer(s) you choose

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Is there such a thing, or a specific term for "break before make" relay that can delay between breaking and making connection?

It sounds as though you are looking for a relay with "centre-off" contacts like an on-off-on, three-position toggle switch. If these exist they are very rare as most relays have only two states, on-off. To do what you are asking would require two coils in the one relay to pull the contacts either way from the centre position.

It's not clear why you think you need this arrangement.

schematic

simulate this circuit – Schematic created using CircuitLab

You can do the job with one DPDT (double-pole, double-throw) relay provided that you don't need it to stop in mid-position. Limit switches are required to cut power to the motor at the top and bottom of stroke.

How it works:

  • With the relay in the position shown current flows to the motor through UP LIMIT and returns through DN LIMIT.
  • When the projector is fully up UP LIMIT will be depressed and power to the motor is cut.
  • When the relay is energised both contacts will be switched. Current will now flow through DN LIMIT, through the motor and return via D1.
  • The motor will run until DN LIMIT is depress and will then stop.
  • Meanwhile UP LIMIT will have closed again so when the relay is switched off the screen will run up again.

D1 and D2 neeed to be rated to handle the maximum current of the motor.

If you decide that a manual switch is all that is required then replace RLY1 with a DPDT switch.

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