Inductive load

[yoggi]

Hi,

I want to use two motorized valves to control incoming water, these valves operate at 24VDC W4.

When the valves opens or closes they draw 2 x 222 mA (working current) and 2 x 15 mA when they are not moved (Static current). I assume this means that the motors are only running when the valves opens or closes (and that there is no cause for concern see below).

My question is, should I run the motorized valves on a separate power supply or could LogicMachine5 Reactor IO, the relay and the valves share one if it is large enough?

My concern is that motors are inductive load and might introduce high-voltage spikes that may damage the LogicMachine5 or relay.

I am looking at the Finder 19.21.0.024.0000 relay, from Finders manual I can see that the relay has a built-in Protection and Inductive Circuit. Would adding a diode in proximity to the inductive load or suppression capacitors near the relay for additional protection make sense.

Is this a case of, better safe then sorry, and just use two 24VDC power supply's?

I found this line in LogicMachine5 Reactor IO manual;

”Binary input/Digital output 16 (Configurable). 380 mA continues current on output. Optoislated from KNX/EIB bus. Additional 24V power source is supported.”

I this used for separation of power, like the above problem?

But even with separated power supply one cable needs to connect the relay to LogicMachine5 binary output port so there will not be totally separate unless there is built-in separation in the LogicMachine5. Right or wrong?

Regards,

Joachim

[mlaudren]

Hi Joachim,

I would recommand to use 1 PSU for command and 1 for control, so both circuit are independent and both would word in parallele.

For what you say about LM I/O, you can use them instead of an external module.
Optoisolated mean that you don't have 'physical' link between the source (LM) and the load (motor). It's an electronic relay to make it simple.

Maybe Admin can confirm that?

[admin]

In case of reactor's the second power supply is only needed where one supply is not enough for 24V outputs. It does not provide output separation. You can try connecting valves directly to 24V outputs since they draw less than the allowed maximum. If this does not work, then you can always install an additional relay. Most DIN-rail relays already have a diode inside for reverse current protection.

[yoggi]

Hi,

Thanks for answering!

The valves are available in an other wiring version BD3 (see attached image) that only needs one switch (SPST) but it uses a little more current. If I am to use the LogicMachines I/O with the B3 wiring how would I wire it up? Can LogicMachines output work as NO, NC and COM? Or would I wire it as I had two separate relays?

Would it make more sense to get the BD3 that only requires one switch?

Are there any advantage with a B3 wiring version(one would think so since it is more complicated)?

Joachim

[admin]

Since LM digital output supplies 24V, you probably need an extra relay. As most relays have both NO and NC connections, you can select any of these two wirings.

[yoggi]

Hi admin,

Could you please clarify your anwser since your first post said to try to use th LMs IO pins and now you are suggesting a relay. Sorry I am just a bit confused.

Joachim

[CHOUAIBOU]

Hi admin,

Could you please clarify your anwser since your first post said to try to use th LMs IO pins and now you are suggesting a relay. Sorry I am just a bit confused.

Joachim

Hi Yoggi,
Inductive load creates current surge as the inductance opposes the interruption of the current. You will probably destroy your LM digital outpout due to over current if you are going to control an important inductive load.
Just use dry contacts (NO/NC) of an extra 24V relay to safely drive your inductive load. Make sure that the nominal current of the relay's coil is lower than the nominal current of the LM digital outputs. Don't make mistake between relay's coil specifications and its dry contacts specifications.

B.R,

Chouaibou.

[yoggi]

Hi Chouaibou,

After reading up on inductive loads I will surly go with a separate relay, maybe you could answer a question I have. Is it possible to power the relay and motor valves from one power supply and the LogicMachine from an other in order to have as much separation as possible (maybe there is no point to have separate power supplies as the relay needs to have contact with one of LogicMachine output pins)?

Somehow the LogicMachine needs to connect to the relay but I cant see this working if they don’t share the same negative. I can see the relay and the LogicMachine powered by one supply and the valves by an other but would this add any protection to LogicMachine?

If I go with a separate power supply for the valves, would there be anny benefits to go down in voltage? The motors comes in 5, 12, 24VDC?

Joachim

[CHOUAIBOU]

Hi Chouaibou,

After reading up on inductive loads I will surly go with a separate relay, maybe you could answer a question I have. Is it possible to power the relay and motor valves from one power supply and the LogicMachine from an other in order to have as much separation as possible (maybe there is no point to have separate power supplies as the relay needs to have contact with one of LogicMachine output pins)?

Somehow the LogicMachine needs to connect to the relay but I cant see this working if they don’t share the same negative. I can see the relay and the LogicMachine powered by one supply and the valves by an other but would this add any protection to LogicMachine?

If I go with a separate power supply for the valves, would there be anny benefits to go down in voltage? The motors comes in 5, 12, 24VDC?

Joachim

Hi Joachim,
The best practice consists on separate power supplies with their respectives protections (controllers power supply / Loads power supply). If the motors comes in 24 VDC, you can power LM and load with the same 24 VDC main power supply for economic reasons. Thus you will have two lines from the main power supply with their respectives protections (LM 24 VDC power supply line and motor/valve 24VDC power supply line). The relay's contacts (NO or NC) prevent the direct link with the 24 VDC of the LM digital output (DO). They are sharing the same negative but the motor or valve's current doesn't flows through the DO of the LM, but through the relay's dry contacts.

You can also use completly separate power supplies as the command sent by the LM through his DO powers the relay's coil. In this scenario, only the relays's coil shares the negative with the DO of LM. The motor will be powered with the second power supply via the relay's contacts. If the voltage of the motor is different to 24 VDC , this solution based on two separated power supply is the only alternative.

B.R,

Chouaibou.

[admin]

The only way to have full separation is to use a relay with a separate power supply.
You can also try a direct connection, where valve is wired in ON state and LM DO acts as a power supply in the schematic. The valves that we have tried had just 2 wires and opened once powered.