Another newbie question

[M5TXJ]

Hello again folks,
Still gathering parts and slowly assembling my Portsdown. I've gone over all the documentation and come up with the following. I've built a triple power supply using the same modules as the Minitiouner, 5v, 5.1v and 8v. My plan is to run the DDS and RF output switch from the 5v, the Pi from 5.1v and the LO filter and filter modulator from 8v (to cut down dissipation in the linear regulators), does this sound reasonable or am I making a big mistake anywhere?
73 Dave.

[g0mjw]

No, but you don't really need two 5V supplies.

Mike

[M5TXJ]

Thanks Mike,
I know it's a little overkill but my thinking was to keep loading on each module to a minimum and also to allow setting for 5.1v actually on the Pi instead of at the regulator.
73 Dave.

[G8GKQ]

Hi Dave

If you're only using the small buck regulators (like on the MiniTiouner) your approach seems very sensible. The challenge is actually getting 5.1V to the RPi under varying loads. I have cut both of my micro-usb leads down so that they are about 7cm long, and put real wires on from there to the power supply which helps.

Dave

[M5TXJ]

Hi Dave,

I've taken a slightly different approach which I hope will be suitable, testing is yet to confirm. I attacked a micro usb lead which had failed with a pair of fine side cutters and clipped all the plastic off the plug. I've soldered some considerably thicker wires direct to the terminals of the plug and encased in adhesive lined heatshrink. I'm going to monitor the voltage at the Pi as it boots, in transmit, with Easycap operating etc etc to see if voltage holds up. In a static test with menu on the TFT there is 0.03v difference between the regulator output and the solder pads on the back of the Pi pcb.

73 Dave

[g0mjw]

I gave up with the USB port entirely and soldered wires onto the bottom of the PI. That worked well and its not too difficult. If you do this make sure the polyfuse is still in line.

Mike