Looking for RELAY Recommendations

Thread Starter

Peter Mpashi

Joined Nov 9, 2023
7
Hello,
I'm looking for a relay, 230VAC, that can work as follows:
Having a constant energizing signal, the normally open (NO) contact closes and then opens (like a push button) while the energizing signal is still on. The normally closed (NC) contact closes and then opens (like a push button) when the energizing signal goes off.
Something like what's shown in the sketch attached, where S is the signal, NO is the "Normally Open" contact and NC is the "Normally Closed" contact.
Your recommendations will be highly appreciated. (Any brand)
 

Attachments

sghioto

Joined Dec 31, 2017
5,392
I don't think there is a single mechanical relay that can do that. I see a possible solution using two relays and some control circuitry.
Is the energizing signal also 230vac? What do the relay contacts control, how much current is involved?
 

Thread Starter

Peter Mpashi

Joined Nov 9, 2023
7
I don't think there is a single mechanical relay that can do that. I see a possible solution using two relays and some control circuitry.
Is the energizing signal also 230vac? What do the relay contacts control, how much current is involved?
Yes the energizing signal is 230VAC. The current involved is not more than 5 Amps. The contacts are controlling the starting and stopping of a motor. I'm only given access to three wires: A common, a starting line (starts the motor when it makes contact with the common) and stopping line (stops the motor when it makes contact with the common). The three wires were on a non-holding, three position rotary switch. I'm supposed to get rid of the rotary switch and let my controller do the switching.
 

Thread Starter

Peter Mpashi

Joined Nov 9, 2023
7
OK. How does your "controller" going to fit into this.
The 24VDC is from a converter parallel to the supply of my controller. If I can have a DC device that can do the kind of switching I want, I can feed it the DC through an AC relay (I have one free Normally Open contact on another relay that I have in circuit already)
 

sghioto

Joined Dec 31, 2017
5,392
Not sure if I understand that fully but presently and from you description of the rotary switch it appears the motor is manually started and stopped and the 230vac is connected constantly to the switch as in this image, correct?
1699632319748.png
 

sghioto

Joined Dec 31, 2017
5,392
OK good. Then you can use the 24 volts DC as the excitation voltage and supply voltage to operate two 24volt dc relays to start and stop the motor. How long will the excitation voltage be present on average between start and stop?
 

Thread Starter

Peter Mpashi

Joined Nov 9, 2023
7
OK good. Then you can use the 24 volts DC as the excitation voltage and supply voltage to operate two 24volt dc relays to start and stop the motor. How long will the excitation voltage be present on average between start and stop?
On average, about 10 minutes.
 

vu2nan

Joined Sep 11, 2014
345
Here's my version, using three relays and an electrolytic capacitor.

1.png

The start pulse is generated when relay K0 is energised and capacitor C1 gets charged through the coil of relay K1.

The stop pulse is generated when relay K0 is de-energised and capacitor C1 gets discharged through the coil of relay K2.

The pulse width is determined by the time constant RC (resistance of the relay coil and capacitance of the electrolytic capacitor).

The 'NO' contacts of K1 and K2 are used to start and stop the motor respectively.

Nandu.
 
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