The two main decisions to make when choosing a power supply are the voltage and total power required. In general, 24V is recommended and a power supply that is rated for at least 20% more than is required provides some headroom.
Minimum and maxium input voltages for Duet boards.
| Minimum input voltage | Max input voltage | |
|---|---|---|
| Duet 3 Mainboard 6HC | 11V | 48V (v1.02 and later), 32V (v1.01 and earlier) |
| Duet 3 Mainboard 6XD | 11V | 30V |
| Deut 3 Mini 5+ | 11V | 25V |
| Duet 3 Expansion 3HC | 12V | 48V (v1.02 and later), 32V (v1.01 and earlier) |
| Duet 3 Expansion 1XD | 12V | 48V |
| Duet 3 Expansion 1HCL | 12V | 50V |
| Duet 3 Toolboard 1LC | 12V | 32V |
| Duet 2 WiFi/Ethernet | 11V | 25V |
| Duet 2 Maestro | 11V | 25V |
Usually, 12V or 24V is used because other components (heaters, fans etc.) are readily available at these voltages. There are three factors that may make 24V preferable to 12V:
The Duet 2 Maestro uses TMC2224 drivers, which work best with lower current motors (hence higher inductance) motors. For this reason, we recommend you use 24V power with the Duet 2 Maestro, especially if the printer is a delta. If you use 12V power, the maximum travel speeds you can achieve may be lower.
Inrush current is the maximum current drawn by an electrical circuit at the time it is turned on. This becomes an issue for boards with lots of capacitance, and especially systems with a number of boards and particularly the Duet 3 M23CL, where there is a large total capacitance.
Generally, this applies if you use a relay between the DC PSU and Vin to control power to the machine, i.e. the power supply is already switched on, and a relay is used to turn on power to the controller boards. It also applies to switching on power to anything with a lot of capacitance across the power lines. It does not apply if power is applied by switching on the power supply, as those are likely to have current limits/soft start/over current protection of some sort.
If your PSU is switching on power with a relay then you should use an inrush current thermistor in series with the Vin line, e.g. https://www.mouser.co.uk/c/circuit-protection/thermistors/inrush-current-limiters/
A single inrush current limiter can be used in series with each pair of relay contacts that switches VIN to one or more boards. If there is more than one relay (or multiple pairs of contacts on a single relay) switching VIN to different boards, each contact pair should have its own current limiter.
The inrush current limiter should be matched to the Duet board or boards in the system. For example, if supplying a single board like a M23CL, the M23CL is fused internally to 2A, so a 2A current limiting thermistor is appropriate. To calculate the inrush current for a larger system, calculate the maximum current for each board supplied via that thermistor (see the 'Total power needed' section above for guidance on how to do that) and add those currents up.
Note that OUT ports on boards should not be used to switch power to other boards directly. This is for 3 reasons:
These can be purchased from MeanWell resellers. The usual electronic component distributors sell similar power supplies.
This is typically the best option if you are comfortable with wiring the mains voltage terminals and with the price. These power supplies are invariably CE-approved and typically include power factor correction. They are available in 12V and 24V versions with a wide range of power ratings. They usually include a voltage adjustment potentiometer.
These are similar to the MeanWell supplies but are made to lower quality standards. They are available very cheaply from eBay suppliers. They usually claim to be CE-compliant, but take this with a pinch of salt because some of them use leaded solder. They include voltage adjustment potentiometers.
Expect these to be less reliable than MeanWell and similar quality PSUs. On the other hand, they may also give years of service, and if they do fail they are cheap to replace. If you choose one of these then it is recommended that you get one with at least 20% more power capacity than you expect to need.
Here's an example of what may happen when they fail. The output inductor was clearly under-rated for this application. The PCB below was badly burned.
Widely available from eBay, Amazon etc. and from PC parts sellers. You can get cheap no-name ATX power supplies, and also ones from a respectable brand such as Corsair.
Advantages compared to the other types listed above:
Disadvantages:
The power rating of an ATX supply is based on a combined load on the 12V, 5V, and 3.3V outputs. So you need to ensure that the 12V output alone is capable of supplying the entire power requirement of your printer.
