Power supply via USB or 2 position plug

Power supply to the ACE PLC is provided via a two position pluggable connector, included with the ACE unit.

All ACEs shipped today are compatible from 5 to 24 VDC.

The ACE can be powered on via:

its USB port (except ACEs with eACE/ACE-7096)
or its 2 position pluggable connector

You can plug both (USB and Power plug) at the same time.

The power supply input of ACE PLCs is protected against reverse voltage. However, reversed polarity is not guaranteed, especially if the USB port is connected.

The input power passes through a switching regulator to be regulated at 5 VDC. Alternatively, the 5V from the USB is passed through a diode to the same point. The 5 V is then regulated to 3.3 V, which corresponds to the internal circuitry.

All the USB cable connection does is connect the PC ground to the PLC ground, and the USB 5V to the regulated PLC 5V, through a diode (which means that if the PLC has a voltage connected through the power connector, the USB voltage is not used). Most PC USB ports are floating (not connected to a hard ground), which means they adapt to the PLC’s ground.

All digitals inputs/outputs are compatible from 5 to 28 VDC whatever the ACE

The pre-regulator inside the PLC regulates a voltage (from 5.1 to 28 VDC) to 5V. It is then down regulated to 3.3V, which all circuits use. The USB power supply goes through a diode, to the same 3.3V regulator.

5 to 24 VDC version : Product reference written in blue

5 VDC version (old one) : Product reference written in black

To connect power, insert the +VDC and the GND connections from a power supply into the plug, as shown in the figure below. When plugged into the PLC’s power connector socket, the +VDC connection is to the right, closest to the PLC corner.

In most cases, connecting also the GND to Ground (the same as the machine and 230 VAC side) solves many problems.

Use the right power supply for PLC : Rectified and filtered

The PLC power supply converts a line voltage, commonly 120 or 240 volts AC, or Alternating Current, into a useable DC, or Direct Current, voltage, commonly 24 volts, to power on the PLC and its components.

Line voltage is stepped down with a transformer, rectified to convert it to DC, filtered with capacitors, and protected during this process. All of this is packed into that small looking power supply

TTL level

If the ACE PLC is connected to USB, it is advisable to supply the PLC with an external 5V power supply at the same time, otherwise the PLC is supplied with 3.8V (there are 2 diodes in series) and there may be detection problems for the 0-5V TTL levels.

Issues : Program stop/loss/reset or damaged PLC

What kind of events could be the cause of this situation?

A high voltage spike can occur on the power supply input, or in the digital output circuit.
- When you start a program in Run mode, there is a bit set in the EEPROM that tells the PLC to restart after a power failure. This bit could have been cleared for various reasons.
Large DC or AC load on the same ACE PLC power line.
- Generally, the problem is feedback from the device (AC motors, AC pump, AC inverter,..) to the PLC power. It more often with DC devices, especially ones that are powered by the same power supply as the PLC.
- In that case, when the device is turned on, there may be a voltage drop to the point that the PLC resets. Also, when the motor is turned off, there may be a voltage spike (especially if snubber diodes are not used) and the voltage spike may cause a PLC reset.
Other cases, when an AC load is switched and the AC supply is the same AC supply that the regulator that powers the PLC uses.
- There can be feedback surges and dips that can do the same thing. This is more rare, but we have seen it. This is especially possible if the AC load is large. For example, a 150W motor isn’t that high of a continuous current, but it could have a high surge current.
Only reset or stop
- You can try updating the firmware. Ask us for the latest version.

How to solve this issue?

Additing a relay on output
- If adding a secondary relay on output relay board doesn’t help suggest that there is feedback in the AC lines.
Add a electrolytic capacitor
- In the range of 100 – 470 uF and 35 or 50V and put it across the input voltage to the PLC. That filters the surge to the PLC and eliminates the problem in the vast majority of the cases.
Add an EMI filter between the suspect device (compressor, powerful motor, etc.) that creates interference on the AC line. The goal is to isolated the suspect device with EMI filter.

Other ways

Disconnecting GND from the HMI RS232 cable the resets can be reduced
24VDC motor drivers which are on the same power supply as the ACE)and the HMI’s TxD/RxD connection
Placing capacitors (100nF MLCC or 10µF Tantal or 220µF Electrolyte capacitors) on all motor drivers and ACEs helped to reduce noise on the 24VDC.
Make a GND connection to a star connection with a central GND sink point near the 24VDC power supply
- Connect the 0V terminal of the 24 VDC power supply to a common ground bus or terminal block. This bus or block serves as the single grounding point for the entire system.
- All other ground connections, such as those from the PLC, HMI, sensors, and other devices, should be tied to this common ground point.
- If the system requires a connection to the building’s earth ground, ensure that the common ground point is properly connected to the earth ground to maintain a consistent reference.

Program doesn’t restart after power lost

Remember that if you leave the ACE running in debug mode, after powering down, it will not restart. So download the program, start it and don’t go into debug mode.

About inductive load

When cutting off an inductive load, a high voltage is generated across the contacts due to the collapsing magnetic field in the inductor. Faraday’s Law of Induction governs this phenomenon, and the voltage across the contacts can be described as:

V = -L * (dI/dt), where
- V: Voltage across the contacts (induced voltage)
- L: Inductance of the load (in Henrys, H)
- dI/dt: Rate of change of current with respect to time (in Amperes per second)

When the circuit is interrupted, the current through the inductor cannot change instantaneously due to its energy-storing magnetic field.
The inductor generates a voltage to oppose the rapid change in current, which can be very large depending on the inductance L and the speed of current interruption dI/dt.
This high voltage can cause arcing across the contacts or damage electronic components if not appropriately managed.
High voltage arcing can damage hardware and interfere with software or firmware.

To mitigate this voltage spike, snubber circuits, freewheeling diodes, TVS, TVSS (Transient Voltage Surge Suppressor), or MOVs (Metal Oxide Varistors), or other methods are used across the inductive load or the switch depending on the applications.

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