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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.
Input power goes through a switching regulator to regulate to 5 VDC.  Alternately, 5V from the USB passed through a diode to the same point.  The 5V is then regulated to 3.3 V, which is what the internal circuitry runs on.

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 a AC Power EMI Filter to the machine’s supply line

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.

Read more about 24V power supply and electrical noise

Extract from the documentation “System Design for Control of Electrical Noise” from Allen-Bradley