## Multi-Tap Transformer PSU Moderators: adafruit_support_bill, adafruit

Multi-Tap Transformer PSU

I am curious to know if (and how many) builders would be interested in replacing the entire power supply unit with a single MULTI-TAP TRANSFORMER. I'm considering buying a prototype at a fab in Akhibara for myself.
If there's enough interest, there can be a WB MMXII variant that will significantly reduce the BOM.

Posts: 5
Joined: Mon Jun 11, 2012 2:49 am

Re: Multi-Tap Transformer PSU

No. Sorry, but to suggest this is indicative of a poor understanding of electronics. That is not necessarily your fault mind, so let me help.

A transformer allows you to convert one AC voltage to another AC voltage, where AC stands for Alternating Current. So a typical example would be a 240V ac to +12V ac, 0V and -12V ac transformer in a home stereo. It takes 240V ac from the mains and converts that into approximately 24V ac. A center tap allows you to get a voltage in between the +12V ac and the -12V ac. Multi-tap transformers simply add more taps to get more points. The are typically used in old fashioned valve-based electronics.

The wavebubble however operates off of a lithium battery, a DC power supply with a voltage of 3.7-4.2Volts. We use special circuits called switch mode power supplies, to "boost" the voltage to 5V, 12V and 28V. These are very efficient, typically 60-90% and are very compact.

To turn the battery voltage into an AC signal requires an inverter, then we feed through a step-up multi tap transformer, this will have taps for 6V, 13V and 30V, the outputs from these are then fed through rectifiers to turn them back to DC and then we need to smooth the resulting voltage to remove ripples. This however does not produce the right voltages because as the current draw goes up then the voltage will drop due to the changes of loading on the transformer, to solve that we will need regulators. This results in a circuit that will be approximately 30-50% efficient, weight about 3 times as much as a wavebubble and cost as much as a wavebubble again.
TheFallen

Posts: 92
Joined: Mon Feb 08, 2010 12:28 pm
Location: UK