So, which are the benefits of using and old AC/DC adapter, anyway? Recycling is perhaps the most important but I have done also for other circuits, such as Arduino, motors, lighting, etc.
Table of Contents
Unregulated Adapters
Important!!
Old electric AC/DC adapters have a higher voltage than its specified on the label. The open circuit voltage (No load for the adapter) is higher because of the voltage drop (due Joule’s Law) that happens when you connect your desired device.
Different Open Circuit Voltage
For example, old Nokia cellphone charger has 9Vdc when unplugged but 3.6Vdc when it’s plugged (therefore, you see the “3.6V battery” label).
Make sure that the circuit that you want to use the adapter, tolerates the open circuit voltage from the old AC DC adapter.
Proportional Voltage Dependency.
Have you checked the actual voltage in your power outlet? In my homeland, we have the “110V” standard. However, when I insert both terminals of the multimeter (switched to 200V in AC mode), I get 127Vac!! And this measure will also vary depending in the hour of the day (122 – 129Vac).
That being said, if your old AC/DC adapter doesn't have a regulator inside, it means the DC output will vary depending on the AC input! This is bad news if your desired device doesn't tolerate wide DC voltage inputs.
What can be done if my old AC DC adapter has unregulated and variable DC output?
Glad you asked!
There is a plethora of devices that takes unregulated, unstable and variable DC voltage input and the transforms it into a regulated and reliable DC output. These devices are called DC DC Converters.
As you may have already guessed, there are many types and they come in many sizes depending on the application. When using an old AC DC adapter, chances are that you are looking for a buck converter which lowers the voltage. For example, from unregulated 12Vdc to regulated 5Vdc.
