12V DPDT relay wiring help

Thread Starter

travy641

Joined Apr 26, 2020
26
Hello,
I am new to electronics so I apologize in advance. I recently bought 3, 12v 30 amp DPDT relays for a remote underwater vehicle (ROV) project that I am working on; however, being new to electronics it has not been fun looking for a wiring diagram. I have 3 bilge pump motors all 12v 5 amps. The 12v battery will be on the small water vehicle with the 3 motors. I will have a tether (CAT5) cable that is 100ft. I want to wire the motors to the relays and be able to toggle the DPDT switch (ON, OFF, ON) at the surface, (opposite end of the battery and motors). When toggling the switches each motor will turn on-off etc. Also, is it possible to wire in a way that UP, the toggle is forward and DOWN is reverse? I've done this with the same DPDT switch connected directly to the motor, but what about controlling relay 100ft away? The reason I will want the motors and batteries together is due to full power as running a 100ft power cable will be added weight and more susceptible to voltage drop? Any ideas would be greatly appreciated. Thanks.

It was hard to follow along with the guide below as I do not want joystick style, just DPDT switches, I have 12v 30 amp relays not micro 12v 5amp. I can't even find the relays he has in the US. One other note is I measured the amp draw of the motors and its about 7.5 - 8 amps; however, when I connect the multimeter to the motor to measure amps, the first initial touch peaks over 10 amps, but it is extremely quick? Would this cause issues if I were to go with a micro 12v dpdt 10amp relay? Thanks.

Also, I tried following a guide here:
http://www.homebuiltrovs.com/howtojoystickhbridge.html
and http://www.homebuiltrovs.com/brcs/BRCSWiringManual.pdf
 

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wayneh

Joined Sep 9, 2010
16,400
Hello,
I am new to electronics so I apologize in advance. I recently bought 3, 12v 30 amp DPDT relays for a remote underwater vehicle (ROV) project that I am working on; however, being new to electronics it has not been fun looking for a wiring diagram. I have 3 bilge pump motors all 12v 5 amps. The 12v battery will be on the small water vehicle with the 3 motors. I will have a tether (CAT5) cable that is 100ft. I want to wire the motors to the relays and be able to toggle the DPDT switch (ON, OFF, ON) at the surface, (opposite end of the battery and motors). When toggling the switches each motor will turn on-off etc. Also, is it possible to wire in a way that UP, the toggle is forward and DOWN is reverse? I've done this with the same DPDT switch connected directly to the motor, but what about controlling relay 100ft away? The reason I will want the motors and batteries together is due to full power as running a 100ft power cable will be added weight and more susceptible to voltage drop? Any ideas would be greatly appreciated. Thanks.

It was hard to follow along with the guide below as I do not want joystick style, just DPDT switches, I have 12v 30 amp relays not micro 12v 5amp. I can't even find the relays he has in the US. One other note is I measured the amp draw of the motors and its about 7.5 - 8 amps; however, when I connect the multimeter to the motor to measure amps, the first initial touch peaks over 10 amps, but it is extremely quick? Would this cause issues if I were to go with a micro 12v dpdt 10amp relay? Thanks.

Also, I tried following a guide here:
http://www.homebuiltrovs.com/howtojoystickhbridge.html
and http://www.homebuiltrovs.com/brcs/BRCSWiringManual.pdf
Do you have a pinout diagram for your relay? What you want to do is not difficult but details are important. How about your toggles?

If you want to control the motors independently, your tether will need one conductor for each motor plus a common, so four conductors. The common could be hot or ground.

Depending on the current required to power your relay coils, I'd be tempted to use a MOSFET to control the coil current. This would practically eliminate any significant current in the tether. You could use a cheap, small MOSFET for that duty because the relays probably don't draw more than 100mA. But you'll need a diode reverse-biased across the poles of the relay coil, to absorb a voltage peak when the coil is turned off and thereby protect the MOSFET. For example, 2N7000 is 36¢ at Mouser, and a 1N4007 diode is 15¢. You'd need one of each for each relay.
 

Thread Starter

travy641

Joined Apr 26, 2020
26
Do you have a pinout diagram for your relay? What you want to do is not difficult but details are important. How about your toggles?

If you want to control the motors independently, your tether will need one conductor for each motor plus a common, so four conductors. The common could be hot or ground.

Depending on the current required to power your relay coils, I'd be tempted to use a MOSFET to control the coil current. This would practically eliminate any significant current in the tether. You could use a cheap, small MOSFET for that duty because the relays probably don't draw more than 100mA. But you'll need a diode reverse-biased across the poles of the relay coil, to absorb a voltage peak when the coil is turned off and thereby protect the MOSFET. For example, 2N7000 is 36¢ at Mouser, and a 1N4007 diode is 15¢. You'd need one of each for each relay.
I do not have a diagram of the pin layout, that was the other issue. I tried following guides online on how to determine what pins are what, but me being new to this stuff caused more confusion. I found the schematic online for that relay; however, not knowing how to read a schematic didn't help. There was no clear indication of pin on that schematic either, such as pin 1,2 NC, 3,4 NO, etc. so it didn't make it any easier. Here is a link to the relay I have; however, my relay does not have PIN layout printed on it like it does in that picture.
http://www.sunshinele.com/htm/power-relay.htm

I plan to use three toggles like the ones below to control 3 motors independently. Also, the amp rating for the relay is 30 amps? Does that mean it can handle up to 30 amps, or that it needs 30 amps to control it?

Also, it doesn't indicate NC, NO, COM etc. least not in a simple fashion, and the toggles I plan to use are these exact ones here. https://www.amazon.com/gp/product/B0002ZPBRA/ref=ppx_yo_dt_b_asin_title_o04_s02?ie=UTF8&psc=1 Thanks.
 
Last edited:

Thread Starter

travy641

Joined Apr 26, 2020
26
I do not have a diagram of the pin layout, that was the other issue. I tried following guides online on how to determine what pins are what, but me being new to this stuff caused more confusion. I found the schematic online for that relay; however, not knowing how to read a schematic didn't help. There was no clear indication of pin on that schematic either, such as pin 1,2 NC, 3,4 NO, etc. so it didn't make it any easier. Here is a link to the relay I have; however, my relay does not have PIN layout printed on it like it does in that picture.
http://www.sunshinele.com/htm/power-relay.htm
Also, it doesn't indicate NC, NO, COM etc. least not in a simple fashion, and the toggles I plan to use are these exact ones here. https://www.amazon.com/gp/product/B0002ZPBRA/ref=ppx_yo_dt_b_asin_title_o04_s02?ie=UTF8&psc=1 Thanks.
 

ElectricSpidey

Joined Dec 2, 2017
1,324
You can determine the pinout of those relays just by looking at them.

The two pins that are 90 degrees from the others are the coil. (12 volt DC)
The set closest to the coil pins are the commons.
The center set is NO.
The end set is NC.

The current rating for the contacts is 30A AC1. (Pic 2)
If you measure the resistance of the coils you can determine the current needed to activate them.
 
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vu2nan

Joined Sep 11, 2014
165
Hi travy641,

1. You have considered only 3 relays. You would need 6 for reversing the motors.
2. The relay contacts are rated for DC1 duty (Non-inductive or slightly inductive loads, resistance furnaces,
heaters). You need contacts rated for DC3 duty (Shunt-motors, starting, plugging , inching, dynamic
braking of motors). However, since you have de-rated the DC1 - 30A relay to use it for a DC3 - 5A
application, it appears to be acceptable.
3. The coil resistance is 120Ω +/- 10%. The DC loop resistance of CAT5 cable is 5.8Ω per 100 feet. The
cable voltage drop of around 0.65V appears to be acceptable.
4. SPDT toggle switches with centre off would suffice.

Here's the schematic for one motor.

untitled5.JPG

The main switch, fuses and freewheeling diodes are not shown.

- Nandu.
 
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Reloadron

Joined Jan 15, 2015
5,667
This is your relay. You only need one relay per motor for FWD / REV but keep in mind there is no Off. Using your relay as in the data sheet attached it would look like this.

Motor Rev Relay.png

Again, the motor is either going forward or reverse. There is no Off. Given a choice at design time I would have just used a simple module H bridge off the shelf. Something like this. They are inexpensive, easy to control and you would have an Off function.

Ron
 

Thread Starter

travy641

Joined Apr 26, 2020
26
Why would you ever run a bilge pump in reverse?
Because they work perfect for ROV applications. You cutt off the red cap, remove the impellers and attach a propeller to the shaft, already waterproof, cheap, and offer perfect amount of power for these applications. Plus all the DIY ROV guides use them, so for a beginner such as my self it was a simpler approach for a first time project of this type.
 

wayneh

Joined Sep 9, 2010
16,400
Because they work perfect for ROV applications. You cutt off the red cap, remove the impellers and attach a propeller to the shaft, already waterproof, cheap, and offer perfect amount of power for these applications. Plus all the DIY ROV guides use them, so for a beginner such as my self it was a simpler approach for a first time project of this type.
Ok, I own one bilge pump and it’s function is ... bilge pump.

So reversibility is part of the plan? I was wondering why you chose 3-position toggles.
 

Thread Starter

travy641

Joined Apr 26, 2020
26
Ok, I own one bilge pump and it’s function is ... bilge pump.

So reversibility is part of the plan? I was wondering why you chose 3-position toggles.
Yeah, I had no idea that would work like that until I starting researching the building of one. Yes reversibility is part of the plan if possible. I am brand new to electronics so, wiring it is become really dificult for me. After all that's why I am here. By the way thanks for all your help.
 

Thread Starter

travy641

Joined Apr 26, 2020
26
Hi
This is your relay. You only need one relay per motor for FWD / REV but keep in mind there is no Off. Using your relay as in the data sheet attached it would look like this.

View attachment 205583

Again, the motor is either going forward or reverse. There is no Off. Given a choice at design time I would have just used a simple module H bridge off the shelf. Something like this. They are inexpensive, easy to control and you would have an Off function.

Ron
Hi Reloadron,
Where do the coils (7,8) get connected to?
 

Thread Starter

travy641

Joined Apr 26, 2020
26
Hi travy641,

1. You have considered only 3 relays. You would need 6 for reversing the motors.
2. The relay contacts are rated for DC1 duty (Non-inductive or slightly inductive loads, resistance furnaces,
heaters). You need contacts rated for DC3 duty (Shunt-motors, starting, plugging , inching, dynamic
braking of motors). However, since you have de-rated the DC1 - 30A relay to use it for a DC3 - 5A
application, it appears to be acceptable.
3. The coil resistance is 120Ω +/- 10%. The DC loop resistance of CAT5 cable is 5.8Ω per 100 feet. The
cable voltage drop of around 0.65V appears to be acceptable.
4. SPDT toggle switches with centre off would suffice.

Here's the schematic for one motor.

View attachment 205559

The main switch, fuses and freewheeling diodes are not shown.

- Nandu.
Hi Vu2nan,
For the cat5 cable would i connect a pair, 2 wires out of the 8 for cat5 to the coils, and other end to the switch? This part of the wiring gets confusing to me? Do i need to use more than 2 wires for power etc. And if so how do I do that if the battery is on board and no batteries at the surface, or would i need a battery at the surface as well? Thanks.
 

Reloadron

Joined Jan 15, 2015
5,667
Hi

Hi Reloadron,
Where do the coils (7,8) get connected to?
However you planned to power the relay coils. Like I mentioned when the relay is deenergized the motor runs one direction, when you energize it runs the opposite direction. There is no Off other than you removing power. If I were doing this I would not have chosen relays but went with an H bridge like I linked to. How do you plan to power everything since it can be 100 feet below the surface? Guessing batteries and you need to look at how much power things use. While a 12 volt 5 amp motor is not much that is only about 1 hour run time on maybe a 12 volt 7 AH battery.

In the interest of power I would keep the batteries with the motors they supply. When choosing CAT 5 cable keep in mind all CAT 5 is not created equally.

"Cat5e cables usually run between 24 and 26 AWG, while Cat6, and Cat6A usually run between 22 and 26 AWG. One of the newest types of Ethernet cables on the market, Slim Run Patch Cables, actually have a 28 AWG wire".

Ron
 

Thread Starter

travy641

Joined Apr 26, 2020
26
However you planned to power the relay coils. Like I mentioned when the relay is deenergized the motor runs one direction, when you energize it runs the opposite direction. There is no Off other than you removing power. If I were doing this I would not have chosen relays but went with an H bridge like I linked to. How do you plan to power everything since it can be 100 feet below the surface? Guessing batteries and you need to look at how much power things use. While a 12 volt 5 amp motor is not much that is only about 1 hour run time on maybe a 12 volt 7 AH battery.

In the interest of power I would keep the batteries with the motors they supply. When choosing CAT 5 cable keep in mind all CAT 5 is not created equally.

"Cat5e cables usually run between 24 and 26 AWG, while Cat6, and Cat6A usually run between 22 and 26 AWG. One of the newest types of Ethernet cables on the market, Slim Run Patch Cables, actually have a 28 AWG wire".

Ron
Yeah, I'm very firmiliar with cat cable types. The cat5e cable I am using is 24awg. I have a 12v 7ah battery on board with the motors, I wanted the cat5 cable to act as the tether, with the switch at the surface, so when flipping the switch it will activate the relay and power on the motor. This way I have full power to the motors and not roughly half due to running a power wire out 100ft. I am just having a heck of a time figuring out how to set it up so it will activate the relay like I just described. Hopefully what I explained makes sense. Thanks.
 
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