circuit to ensure only one relay is on at a particular time

Thread Starter

jkhalid

Joined Aug 19, 2018
1
I am trying to turn on/off some circuits from relays using a microcontroller. Each day at a specific time the circuit turn on and at a specified off time the circuit turns off. Each of the circuits is for each day. For example, day 1: circuit 1 turns on, day 2 for circuit 2, day3 for circuit 3, .. day 6 circuit 6 and then day7 circuit 1 and it goes on..
The connection is as : microcontroller -> relays -> external circuit
On the software side I will program the microcontroller to turn on/off the circuits at the respective date. The on/off times will be specified by the user.

But I want to be able to do it on the hardware side such that when circuit 1 is on, all the other circuits are not getting power and hence they will not turn on. When one circuit is on, the rest should be off. I want some kind of redundancy on the hardware side also.

I want to have some ideas on how i can achieve this task.

Thank you
 

MaxHeadRoom

Joined Jul 18, 2013
22,375
You need a hold off relay which is picked up by any of the other relays, the hold off relay will have a N.C. contact in each of the operating relays coil, across this N.C. contact is a N.O. retaining contact of the relay that is operating at that point.
The hold off relay will be picked up by a N.O. contact on any operating relay.
All other relays will be held off.
Max.
 
Last edited:

GetDeviceInfo

Joined Jun 7, 2009
1,754
You need a hold off relay which is picked up by any of the other relays, the hold off relay will have a N.C. contact in each of the operating relays coil, across this N.C. contact is a N.O. retaining contact of the relay that is operating at that point.
The hold off relay will be picked up by a N.O. contact on any operating relay.
All other relays will be held off.
Max.
It would be fun watching you draw this schematic
 

danadak

Joined Mar 10, 2018
4,057
Switching DC loads ? If so use a muxed A/D to scan load energized and
turn off the others. There are controllers with muxed A/D on them. In fact
ones with scanning comparators with front end muxes as well.

If AC loads use a set of relay contacts to scan with UP the state of relay.

Regards, Dana.
 
Last edited:

crutschow

Joined Mar 14, 2008
26,416
Would it not be sufficient just to scan the state of the relays as danadak suggested?

Otherwise you could use some variation of a radio-pushbutton circuit to insure only relay is on at a time.
 

Bernard

Joined Aug 7, 2008
5,743
Otherwise you could use some variation of a radio-pushbutton circuit to insure only relay is on at a time.
Here is a logic version of a lock out circuit. 555s used as relay drivers. New application would drop RC timing, day 1 ON pin isLock out #2 00001.jpg a negative pulse on A-2, off pin a + pulse on A-6. When A is on no action possible on B or C.
 
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