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2 latching relays, 2 pushbuttons, 2 dc 5 Volt motors and 4 limit switches

Holz1

Jul 19, 2022
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Hello FORUM,

On the forum I have seen a lot of posts with respect of dc motors and limit switches operated by SPST and DPDT relays but not for operation with latching relays which I am using.

I am not a skilled electronic technician but a hobbyist.

Enclosed you will find a circuit diagram for the running and stopping of 2 5 volt dc motors controlled by /with 2 HONGFA latching relays.

Explanation of circuit diagram

Activation of PB1 switches ON relay 1 and 2 and both the 5 volt DC motors are running CW until the GREEN activators are reached. The motors are deactivated.

Activation of PB 2 the relay 1 and 2 are switched ON and the motors start running CCW until the RED activators are reached. The motors are stopped.

Problem:
It does not work. I have made the circuit with only 1 latching relay and it works/operates.
I think the problem are the diodes and the way they should be placed. And here stops my knowledge and I have tried several positions but I cannot find the solution.

Can somebody help me with the correct circuit

Thanx in advance

Harry
 

Attachments

  • 2 DC Motors  2 Bistable LATCHING relay .png
    2 DC Motors 2 Bistable LATCHING relay .png
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CircutScoper

Mar 29, 2022
300
Joined
Mar 29, 2022
Messages
300
Hello FORUM,

On the forum I have seen a lot of posts with respect of dc motors and limit switches operated by SPST and DPDT relays but not for operation with latching relays which I am using.

I am not a skilled electronic technician but a hobbyist.

Enclosed you will find a circuit diagram for the running and stopping of 2 5 volt dc motors controlled by /with 2 HONGFA latching relays.

Explanation of circuit diagram

Activation of PB1 switches ON relay 1 and 2 and both the 5 volt DC motors are running CW until the GREEN activators are reached. The motors are deactivated.

Activation of PB 2 the relay 1 and 2 are switched ON and the motors start running CCW until the RED activators are reached. The motors are stopped.

Problem:
It does not work. I have made the circuit with only 1 latching relay and it works/operates.
I think the problem are the diodes and the way they should be placed. And here stops my knowledge and I have tried several positions but I cannot find the solution.

Can somebody help me with the correct circuit

Thanx in advance

Harry

Hi, Harry. Question: Your schematic suggests that your "actuator" limit switches are normally closed, and open (breaking the circuit) when your motors arrive at the limit of their motion cycle. Is this true, or are they normally open and close at motion limit?

If the former is true, then I don't understand how they can control latching relays.
 

Minder

Apr 24, 2015
3,478
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Messages
3,478
I didn't study the circuit in detail, but it is common to use NC L.S with a diode rectifier across the switch, When the actuator reaches its limit, the switch opens and disconnects the motor, but the L.S. diode polarity "arms" it for the opposite direction.

upload_2022-7-19_11-10-41.png
 

Attachments

  • ActualtorLS.jpg
    ActualtorLS.jpg
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Last edited:

Bluejets

Oct 5, 2014
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6,901
Unusual to use latching relays to begin with as any fault requires activation of certain sections of the control circuit to shut the motor down rather than fail safe where things just stop with control circuit deactivated.
Limit switches as a result of the above, instead of being in the control circuit where they belong, end up in the motor power supply, bad design.

Suggestion for future would be get one unit working first before adding complications and possible errors with two systems.
 

CircutScoper

Mar 29, 2022
300
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Messages
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Latch.GIF

Why not just one relay?

Hello FORUM,

On the forum I have seen a lot of posts with respect of dc motors and limit switches operated by SPST and DPDT relays but not for operation with latching relays which I am using.

I am not a skilled electronic technician but a hobbyist.

Enclosed you will find a circuit diagram for the running and stopping of 2 5 volt dc motors controlled by /with 2 HONGFA latching relays.

Explanation of circuit diagram

Activation of PB1 switches ON relay 1 and 2 and both the 5 volt DC motors are running CW until the GREEN activators are reached. The motors are deactivated.

Activation of PB 2 the relay 1 and 2 are switched ON and the motors start running CCW until the RED activators are reached. The motors are stopped.

Problem:
It does not work. I have made the circuit with only 1 latching relay and it works/operates.
I think the problem are the diodes and the way they should be placed. And here stops my knowledge and I have tried several positions but I cannot find the solution.

Can somebody help me with the correct circuit

Thanx in advance

Harry
 
Last edited:

Bluejets

Oct 5, 2014
6,901
Joined
Oct 5, 2014
Messages
6,901
No worries...thought they were standard relays..... nothing marked so who would know.
Limits are still in the motor power lines and no way to stop except manually press limit.
Soon as released it would run again.
Still an upshot design......
 

CircutScoper

Mar 29, 2022
300
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...
Limits are still in the motor power lines and no way to stop except manually press limit.
Soon as released it would run again...

Que anon. When a limit switch is pushed open, the corresponding motor stops, holding the limit open and the motor stopped.
 

CircutScoper

Mar 29, 2022
300
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No worries...thought they were standard relays..... nothing marked so who would know.
Limits are still in the motor power lines and no way to stop except manually press limit.
Soon as released it would run again.
Still an upshot design......

You can do it with a standard relay.

Latch.GIF
 

Holz1

Jul 19, 2022
33
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Jul 19, 2022
Messages
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Hi, Harry. Question: Your schematic suggests that your "actuator" limit switches are normally closed, and open (breaking the circuit) when your motors arrive at the limit of their motion cycle. Is this true, or are they normally open and close at motion limit?

If the former is true, then I don't understand how they can control latching relays.
Hi, Harry. Question: Your schematic suggests that your "actuator" limit switches are normally closed, and open (breaking the circuit) when your motors arrive at the limit of their motion cycle. Is this true, or are they normally open and close at motion limit?

If the former is true, then I don't understand how they can control latching relays.
Hi, Harry. Question: Your schematic suggests that your "actuator" limit switches are normally closed, and open (breaking the circuit) when your motors arrive at the limit of their motion cycle. Is this true, or are they normally open and close at motion limit?

If the former is true, then I don't understand how they can control latching relays.

Good morning.
Every circuit has a variety of approaches of problems. I like to solve the problem how to connect the 2 pushbuttons with 2 latching relays activated at the same moment. pushbutton 1 will activate 2 relays and pushbutton 2 will switch back the 2 relays. This is not working in my tests.

The actuators are pushing down the leafswitches which are NC and the motors are stopped.
Because the 2 motors have not the same speed, I cannot use 1 relay in my situation. Each motor has to be controlled by 1 relay . So 2 relays will activated at the same time by 1 pushbutton as described in the diagram.
I use latching relays because they hold their position until the next PB is activated.
 

Holz1

Jul 19, 2022
33
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You can do it with a standard relay.

View attachment 55666
Is it possible to draw the above circuit but then with the 2 latching relays and 2 pushbuttons Normalle Open (NO).?

PS. I tried my circuit with 2 PB and 2 relays without the motors but only with leds. This is working, but when I connect the motors with leafswitch it does not operate as I expected. The problem are the diodes and to place these in the circuit.
 
Last edited:

CircutScoper

Mar 29, 2022
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Is it possible to draw the above circuit but then with the 2 latching relays and 2 pushbuttons Normalle Open (NO).?

PS. I tried my circuit with 2 PB and 2 relays without the motors but only with leds. This is working, but when I connect the motors with leafswitch it does not operate as I expected. The problem are the diodes and to place these in the circuit.

If you want to unnecessarily waste a relay, go for it.
 

CircutScoper

Mar 29, 2022
300
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Is it possible to draw the above circuit but then with the 2 latching relays and 2 pushbuttons Normalle Open (NO).?

PS. I tried my circuit with 2 PB and 2 relays without the motors but only with leds. This is working, but when I connect the motors with leafswitch it does not operate as I expected. The problem are the diodes and to place these in the circuit.

Oh, okay. Maybe you live in a land where latching relays are cheaper than diodes.

Latch.GIF
 
Last edited:

Holz1

Jul 19, 2022
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If you want to unnecessarily waste a relay, go for it.
Now, I am intrigued! You mean there is a solution to switch with only DIODES and ZERO relays? What are the white rectangles near the diodes indicated by the S (set) and R (reset)? Resistors?
 

Holz1

Jul 19, 2022
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Now, I am intrigued! You mean there is a solution to switch with only DIODES and ZERO relays? What are the white rectangles near the diodes indicated by the S (set) and R (reset)? Resistors?
Looking at the new diagram, I see you switch the 1st relay with diodes through + 5 Volts and leaving the fly-back diodes for 2nd relay. Can you explain to me in simple words why?
 
Last edited:

CircutScoper

Mar 29, 2022
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Looking at the new diagram, I see you switch the 1st relay with diodes through + 5 Volts and leaving the fly-back diodes for 2nd relay. Can you explain to me in simple words why?

Because both pairs of relay coils are connected in parallel, one pair of diodes serves both.
 

CircutScoper

Mar 29, 2022
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Now, I am intrigued! You mean there is a solution to switch with only DIODES and ZERO relays? What are the white rectangles near the diodes indicated by the S (set) and R (reset)? Resistors?

The rectangles represent the relay coils, just as rectangles do in your diagram.
 

CircutScoper

Mar 29, 2022
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Now, I am intrigued! You mean there is a solution to switch with only DIODES and ZERO relays?

Hereabouts you can buy ~100 1Amp diodes for the price of 1 dual-coil latching relay. Therefore saving 1 relay at the cost of adding 4 diodes, as my design does, is something anyone with aspirations to become (or act like) an engineer should be interested in.
 

Holz1

Jul 19, 2022
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Because both pairs of relay coils are connected in parallel, one pair of diodes serves both.
Thnak you very much. I will try it to day and I will disconnect the pair of diodes from the second relay as you suggest.
I keep you posted.
 

Holz1

Jul 19, 2022
33
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Is it possible to draw the above circuit but then with the 2 latching relays and 2 pushbuttons Normalle Open (NO).?

PS. I tried my circuit with 2 PB and 2 relays without the motors but only with leds. This is working, but when I connect the motors with leafswitch it does not operate as I expected. The problem are the diodes and to place these in the circuit.
Now I understand this drawing in conjunction with the drawings containing 2 relays. I will 1st build this one.
Thanx!
 
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