There are plans for 5 daughter board variants:

1. Generic microUSB interface. 5V in, 5V out.
2. Discrete voltage regulator (see previous log.) 7.5 - 12V in, 5.3V out, or 20V in 15V out.
3. SOT89 LDO regulator. 7.5 - 12V in, 5.3V out.
4. SOIC8 LDO regulator. 7.5 - 12Vin, 5.3V out, or 20V in and 15V out.
5. Switching regulator (buck converter). 7.5 - 12V in, 5.3V out.

They all fit onto the 13x13mm daughterboard dimension. If none of these tickle your fancy, then make your own.

Generic micro-USB:

There's not much going on here. Just a standard micro USB (B-type) mounted on the edge of the daughter board as so:

The 5V output connects to the probe power supply inputs through the header pins. The connector is an Amphenol 10103594-0001LF -- hopefully easy to get and not too expensive. This is probably what I will use for my slim probes since I have jiggered my wall adapters to output 5.25VDC.

SOT89 LDO Daughter Board:

This board uses the same LDO as what Paul used for his original probe. The LDO is an XC6216 adjustable voltage regulator IC, that comes in a SOT89-5 package.

There are a few alternative LDO ICs that will work as well, if you can't get the XC6216. 

The SOT89 should be able to handle the power dissipation easily.

SOIC8 LDO Daughter Board:

I used a widely available LP2951 voltage regulator that comes in a SOIC package option. It's a bit large, but it fits. [2025-10-21] Added a better snubber at the input.

There are three main manufacturers: TI, On semi, and Micro Chip. It is relatively inexpensive, around $0.50/each in low quantities.

Buck Converter Daughter Board:

I designed this board just for grins and giggles. It should be much lower power dissipation than the LDO alternatives. But it might be too noisy to be located so close to the probe circuitry. The switching regulator is a Richtek RT8259 (with RyChip RY8310 as a second source.) It switches at 1.2-1.4MHz, which allows for small components.