VFD interface with water pump

There are three ways (that I can think of) that a user would want a water pump to activate. How is each of these wired within the enclosure?

  1. Turn the pump on/off when power to the VFD turns on.
    I think I know this one: connect relay terminals (R01A and R01C) to a 24V power source and a 24V contactor to turn on/off the 220V power to the cooling pump. On/off by main power switch.
  2. Turn the pump on/off when power to the spindle is on/off
  3. Turn the pump on with the spindle, but not off until some time (perhaps 20 min) after the spindle stops. Purpose is to continue cooling a hot spindle but also to keep it cooling during a bit change).

Hey David,

depending on the max. current draw of your pump, you may connect it directly to the Relay output, or if it exceeds the RO1A specification on page -29/30- (PDF page 33/34), you need to contact an external relay that switches the pump on. The specification says: “Contact capacity: 3A / AC250V, 1A / DC30V”. This is a relatively high switching capacity, enough for a pump (but not enough for switching the dust collector or a workshop vacuum cleaner). Is it for the pump for the spindle coolant? If it is an AC 110–250 V pump which draws not more than 3 A current, you can connect the Relay output RO1A and RO1C directly between one wire of the pump and one “hot” contact of the AC wall socket, while the other wire of the pump goes directly to other contact of the AC wall socket directly. If it is a DC max. 30 V pump that draws not more than 1 A current, you need a power supply for providing the DC power for your pump and you wire it the same way as above, but instead of connecting it to the AC wall socket, you use the two wires from the DC power supply.

Regarding triggering and duration of the pump being activated, this is set with P0g.03 on page -79- (PDF page 84). You can set the condition to “spindle running” by setting P06.03 (Relay RO1 output selection) to “1” (In running) which would be the best choice in my opinion. This corresponds to your scenario Nr. 3. For the duration with which the spindle shall further be cooled after it was stopped, you can set P06.11 “Relay RO1 switch-off delay” to a value between 0 s and 50 s.

I took this information from Hitachi S1 Series VFD Manual (PDF).

Yes, the manual describes setting a delay time for shut-off, but no more than 50 sec. Are there other devices that can be added to an enclosure for the purpose that could give more time?

The pump is for the spindle cooling and uses 220v. Its manual says it only draws 0.5 amps.

Hey David,

yes, you could add a timer module that are available everywhere. But since they work with low DC voltages, you would need to also use an additional external relay that would switch the 220 V pump on and off. The timer module would switch the control input of the external relay, and the timer module would be triggered by the relay output of your VFD as already mentioned above.

Usually I would say a module based on a programmable interval timer like the ubiquitous NE 555 would be totally sufficient, but I have learned that nowadays, you get a microcontroller-based module at the same price :slight_smile:. So you could buy a TRM01 timer module (a timer module based on the microcontroller STC 8G1K08, which is a Intel MCS-51 (8051) specimen) and is programmed to allow up to 120 s delay. I would choose the 24 V version as this voltage is the most common for accessories in a VFD control cabinet. There was a thread about exactly this → here the other day. It was for a Huanyang VFD, so the relay pins have other labels than your Hitachi S1, but you see how it works. You use the normally open (NO) contact of the VFD’s relay output and connect it to (e.g. the VFD’s internal) 24 V, and you connect the common contact to trigger the X1 input of the TRM01 module. The advantage of this module is that it already contains the external relay that can switch 250 V AC 10 A! So you could connect your pump directly to it. The module can have four modes of operation, of which one is to insert a delay before shutting the load (your pump) off.

Note that on the thread mentioned, the forum user wanted to use a solid state relay (SSR), here the ubiquitous FOTEK SSR-40 as described by buildbotics on this page, but there are some disadvantages in using a solid state relay compared to a “true” electromagnetic relay. The advantage of SSrs are that they need only an extremely small control current to be switched on or off. But their disadvantages are that they are made of only semiconductors, so on overload they can be destroyed or start malfunctioning easily without you noticing it, and the other disadvantage is that to hold their state, they need a relatively high switched current on their load side, of at least approx. 100 mA, which means if the load you switch draws less current than this, you cannot be sure that the switching “on” state of the relay will persist, or the relay reverts its state back. An electromagnetic relay can switch much lower load currents reliably, and it is either functional or broken. And usually they have a transparent housing where you can see the physical state of the contacts (and hear them, they “click” when switched). SSRs don’t “click”.

But the real problem with the SSR described, the FOTEK SSR-40, is that
you only find counterfeit FOTEKs on the market. I did not find an original.

Anyway if you choose the TRM01 module, it already has a “true” electromagnetic relay onboard (the blue box on the pcb) that will switch a load of max. 250 V AC / 10 A. Just be sure to select the version for 24 V for the control circuit and the microcontroller supply.

Otherwise, when using just a NE555-based timer, when selecting an external relay, be it a solid state or an electromagnetic relay, you need one that is rated on its control input by preferably 24 V DC and that can switch a load of at least 220 V AC / 0.5 A (which is your pump).

If one day you want to also switch your dust collection system or workshop vacuum cleaner, it could be that 10 A are not enough. In this case you would need an additional relay with that capability, but with the TRM01 module, you already can switch 250 V AC / 10 A with the blue onboard relay.

With my upgrade i ordered an IoT device from PWN.- It allows for automatic synchronization of two devices. As soon as the spindle starts spinning- the water pump and the dust collection then kick-on and they stay on until the spindle slows down.
I am not too tech savvy - and this worked very simply without any complications.

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Hey David,

didn’t know that PwnCNC also offers these now.

I know them from this URL: External IoT relay

It switches loads on four NEMA 5-15 connectors with 120 V AC with total current max. 12 A . The triggering current of the control circuit is extremely small so that an Arduino or the buildbotics controller can control the relay directly.

Many people in this forum who have 120 V in their country use this relay which was propagated early in this forum, in this thread: