I do not take any responsibility for personal harm or property damage caused by building or using this project. Make sure to read my safety recommendations below.
This project allowed me to power up devices through their DC jack using my bench power supply banana plugs. I highly doubt you found this page without going through my video first, so you probably already know what I'm talking about!
I mainly use this for powering retro consoles through their DC jacks, because of their reduced current draw and voltage requirement. It might be possible to power laptops too but only while idling, as they tend to have a much higher current draw which could exceed the capabilities of the board. Also, some laptops can detect it's not the original charger and may prevent charging the battery. Sometimes the laptop might still power on, just no charging will happen.
The polarity switch is useful for devices like the Sega Game Gear which require a different connector polarity based on their region, but generally speaking retro consoles come from a time where it was very likely to find center negative connectors. When working on a lot of them you might find yourself needing to switch polarity in between devices.
This adapter can be powered via banana plugs (male). It can work with any universal connector set that can be powered via 5.5mmx2.1mm DC plugs (male), as long as you own a male-to-male 5.5mmx2.1mm barrel plug adapter.
- Male-to-male 5.5mmx2.1mm barrel plug adapter WARNING: THIS CABLE IS ONLY RATED FOR 12V @ 3A
- Universal connectors set WARNING: THESE CONNECTORS ARE ONLY RATED FOR 90W
- If you want a better male-to-male adapter you can build it using solderable 5.5mmx2.1mm DC plugs and solder them to two wires. You can find 24V 3A ones on some websites.
Assembling this should be very straightforward, there are markings on the board that will help you place every component down properly.
- LED orientation is marked on the board like a regular diode.
- The resistors have no required orientation
- The electrolytic capacitors have the negative side marked on the board.
- The voltage regulators are TO-92 packages and they have the flat side marked down on the board.
- The DC socket cannot be placed in the wrong way.
- The polarity switch has the actuator drawn on the board but you can also rotate it to make it harder to be accidentally flicked. If you somehow prefer you can even mount it on the other side of the board.
- The banana sockets are slightly more complicated, you can see a bit of how I did in my video for this project. I recommend making sure the solder starts slightly poking out of the holes on the other side of the board, acting like tiny rivets. This is to ensure a very strong mount that is taking advantage of the entire board strength.
You can download the bill of materials from here
You can order the PCB directly from PCBWay, or you can download the gerber files required for manufacturing.
I recommend choosing a white or red solder mask color, as it boosts the red light coming from the LEDs.
- Read and become familiar with the safety information and power ratings down below
- Insert the positive banana plug coming from the bench power supply in the adapter's positive (red, or marked V+) banana socket
- Insert the negative banana plug coming from the bench power supply in the adapter's negative (black, or marked V+) banana socket
- Insert one end of a male-to-male 5.5mmx2.1mm barrel plug adapter inside the adapter's DC socket marked J3
- Attach the connector you need at the other end of the male-to-male barrel plug adapter
- Ensure the adapter board is not touching and cannot touch any conductive object or surface
- Enable power output from the bench power supply to the adapter
- Select appropriate connector wiring using the selection switch
- Plug the connector in the device which must be powered
- Do not reverse the positive and negative banana plugs, the board might not survive that
- Set overvoltage protection on your bench power supply at 30V
- Optionally set a current limit or overcurrent protection of 3A on your bench power supply when using this adapter, or always be ready to cut power to the adapter board immediately
- Follow the handling recommendations listed below
- Do not exceed the power rating listed below
- Keep the board unpowered when not in use to avoid accidental shorts
The bare adapter board must be kept away from any conductive object or surface. It has many easy to short points, and it would be best to have an enclosure for it. However, you must keep in mind that I have not designed such an enclosure yet, and it is currently not available.
My recommendations for it would be to use simple brass standoffs, with two simple laser-cut acrylic plates above and below. If you have a 3D printer you can probably design yourself a plastic enclosure with some slots to insert clear plastic sheets of any kind.
If you can't make yourself an enclosure, you will have to pay very close attention to where you place the board, or even wrap it in kapton tape if you're particularly forgetful about this kind of stuff.
All ratings discussed here only refer to this adapter board. This doesn't apply to any kind of cable, adapter, or connector that you use with this board. Using wires, adapters, or connectors with an inferior rating can cause them to melt or catch on fire if their own rating is exceeded.
24V @ 3A
I naturally don't have specific ratings for this board as several factors can affect it, nor have I performed any testing.
| Part # | Description | References | Power Rating |
|---|---|---|---|
| SK22D15L5 | DPDT Polarity Switch | SW1 | 50V @ 3A (150W) |
| DC-044K-D020 | DC Socket | J3 | 24V @ 7A (168W) |
| HT7525-1 | LDO Voltage Regulator | U1, U2 | 30V |
| KS106M050C07RR0VH2FP0 | Electrolytic Capacitor | C1, C2, C3, C4 | 50V |
- Exceeding 24V WILL EVENTUALLY damage the DC Socket or heating it up more than it should
- Exceeding 30V WILL damage the LDO Voltage Regulators, which might end up causing further damage to the adapter or whatever you're powering with it.
- Exceeding 50V WILL EVENTUALLY damage the Polarity Switch or heating it up more than it should
- Exceeding 50V WILL blow up the electrolytic capacitors, which could end up causing personal injury
- Exceeding 3A WILL EVENTUALLY damage the Polarity Switch or heating it up more than it should
- Exceeding 7A WILL EVENTUALLY damage the DC Socket or heating it up more than it should
- Exceeding 150W WILL EVENTUALLY damage the Polarity Switch or heating it up more than it should
- Exceeding 168W WILL EVENTUALLY damage the DC Socket or heating it up more than it should
- Exceeding ANY OF THESE, MAY cause personal injury, property damage, or start fires.
- The board MIGHT tolerate exceeding Wattage or Amperage ratings, it MIGHT tolerate exceeding 24V, but it will NEVER tolerate exceeding 30V.
- Monitor the temperature of the adapter board at all times while exceeding any limit, and make sure to be ready to cut power immediately.
| Dimension | Value | Notes |
|---|---|---|
| Board Size | 66mm x 66mm | |
| Hole Pattern Spacing | 54mm | |
| Hole Distance From Center to Board Corner Edges | 6mm | Measured before adding fillets |
| Board Fillet Radius | 9mm | |
| Mounting Hole Diameter | 3.2mm | |
| Mounting Hole Conductive Ring Thickness | 1.2mm |