Relay replacement ideas -- RF receiver to control 24v eletromagnectic.

Thread Starter

Link068

Joined Apr 10, 2017
31
HI,

I currently have a relay and a receiver issue. I am wanting a RF receiver to control 24v, however the relay will always draw current from receiver even when pin has not been activated.

Does anyone have an other circuit ideas to replace the relay element?

I was thinking a bjt...etc
 

Reloadron

Joined Jan 15, 2015
7,501
As drawn if the Rocket Switch and the RF Receiver switch are ever in the wrong positions you have 6 volts to ground. As drawn the SSR 40 A DD can't draw any current when the RF Receiver switch has the common input going to ground.
I am wanting a RF receiver to control 24v, however the relay will always draw current from receiver even when pin has not been activated.
Looking at the drawing I see no way that can happen if the circuit is per the drawing. The SSR is drawn as a relay, is it a relay or SSR (Solid State Relay)?

Ron
 

ScottWang

Joined Aug 23, 2012
7,397
If your circuit is match the real connections then the wiring of relay of RF receiver maybe wrong, you can't connected another pin to Gnd and it will make the 6V battery shorted.

Another control circuit using 4.5V logic level N type MOSFET to control the electromagnetic below, D1 you can using some other flywheel diodes for D1, the draw current of electromagnetic only 0.24A, it is not that much, so when you choose the N type MOSFET is more easier, rated current 2A is enough.

RF receiver to control 24v electromagnetic_Link068_ScottWang.png
 

Thread Starter

Link068

Joined Apr 10, 2017
31
As drawn if the Rocket Switch and the RF Receiver switch are ever in the wrong positions you have 6 volts to ground. As drawn the SSR 40 A DD can't draw any current when the RF Receiver switch has the common input going to ground.

Looking at the drawing I see no way that can happen if the circuit is per the drawing. The SSR is drawn as a relay, is it a relay or SSR (Solid State Relay)?

Ron
The receiver represents high and low of the output pin. In the diagram its in the off position. Rocket switch is used as an external power on/off switch.
 

Thread Starter

Link068

Joined Apr 10, 2017
31
If your circuit is match the real connections then the wiring of relay of RF receiver maybe wrong, you can't connected another pin to Gnd and it will make the 6V battery shorted.

Another control circuit using 4.5V logic level N type MOSFET to control the electromagnetic below, D1 you can using some other flywheel diodes for D1, the draw current of electromagnetic only 0.24A, it is not that much, so when you choose the N type MOSFET is more easier, rated current 2A is enough.

View attachment 145582
Thanks for that Scott. I had the same circuit in mind however just swapping the mosfet for a transistor since current draw will be <1amp. I haven't had an experience with a fett since we haven't covered them in class yet.

Would your circuit prevent current to the relay when receiver pin is inactive?

Apologizes, the negative of the relay is connected to the negative of the 6v battery.

Also why would you use a flywheel diode instead of regular diode? Could you explain why you have a diode across the load?

Cheers,
 

ScottWang

Joined Aug 23, 2012
7,397
Would your circuit prevent current to the relay when receiver pin is inactive?
If the receiver is inactive then the Vgs of MOSFET will be connected to Ground, so there is no Ids and it won't work that it is at the OFF status, the electromagnetic also OFF, there is no current flows though the electromagnetic.

Also why would you use a flywheel diode instead of regular diode?
That is depends on the switching speed of coil, here is the electromagnetic, normally use 1N4002~4007 is ok, use the rated voltage of diode has 4 times of the voltage(+24V) is better, when you need high speed discharge for the coil then you can use flywheel diode.

Could you explain why you have a diode across the load?
That was used to protects the N MOSFET for the Back EMF of coil.
Back EMF Suppression.
 

Thread Starter

Link068

Joined Apr 10, 2017
31
If your circuit is match the real connections then the wiring of relay of RF receiver maybe wrong, you can't connected another pin to Gnd and it will make the 6V battery shorted.

Another control circuit using 4.5V logic level N type MOSFET to control the electromagnetic below, D1 you can using some other flywheel diodes for D1, the draw current of electromagnetic only 0.24A, it is not that much, so when you choose the N type MOSFET is more easier, rated current 2A is enough.

View attachment 145582
Hi Scott,

What is the use of R1?

Cheers
 

ScottWang

Joined Aug 23, 2012
7,397
Hi Scott,

What is the use of R1?

Cheers
R1 was used for guarantee the Vg has on a ground level whatever Sw1 or Sw2 turn off and that will be turn off the MOSFET and cutoff the Id current, and there is no any current flows through the electromagnetic, the values of R1 can be 4.7K~100K, more less resistor will be draw more current, but it will be good for noise interference, and vice versa.
 
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