Nov 202016

So, I got most of the bits together to build a first power module for the cluster. This is after a mix-up with some of the parts, namely:

  • the 2 and 3-pin KK connectors I ordered just came as housings, no pins.
  • the supplier mixed up my order and sent rubber feet instead of 3-pin KK connector housings.

So I’ve got some 2-pin housings, but no pins … no problem, this was my fault for not checking and I think I’ve found the right pins for the task. I’ve placed a second order for these (along with some other bits to play with).

The rubber feet will be put on one side: I have no immediate use for them, and the supplier has dispatched the 3-pin KK housings already. A mix-up at their end hopefully rectified. So I’ll probably have those early next week, and the pins should arrive Thursday or Friday.

In the meantime though, I rummaged around the junk box and found a 3-pin KK that was snipped off a socket-370 CPU fan. For what it’s worth, the plug it’s connecting to is de-soldered from an old motherboard too.

The purpose of this module is to switch on or off a +12V charging supply… the intent is that to the board, it looks like a MOSFET, with the same control signals one would see. It is intended to be hot-pluggable (in more ways than one).

The red/black Anderson connector is the DC input, which can in theory be up to 16V DC. It passes in through the white Anderson, through both MOSFETs then out the yellow Anderson to the flying lead that will be connected to the +12V bus bar.

A second flying lead allows connection of the 0V supply to the 0V bus bar. I’m deficient in the black wire department, so a scrap length of heavy gauge speaker wire will do here.

I’ll have to work on how to mount those connectors, at the moment they’re just hanging loose which is not good long-term. I’ll probably glue these to a small piece of perspex, drill/tap some mounting holes and screw it down to stop it flapping in the breeze.

Nov 202016

The Yaesu FT-897D has the de-facto standard 6-pin Mini-DIN data jack on the back to which you can plug a digital modem.  Amongst the pins it provides is a squelch status pin, and in the past I’ve tried using that to drive (via transistors) the carrier detect pin on various computer interfaces to enable the modem to detect when a signal is incoming.

The FT-897D is fussy however.  Any load at all pulling this pin down, and you get no audio.  Any load.  One really must be careful about that.

Last week when I tried the UDRC-II, I hit the same problem.  I was able to prove it was the UDRC-II by construction of a crude adapter cable that hooked up to the DB15-HD connector, converting that to Mini-DIN6: by avoiding the squelch status pin, I avoided the problem.

One possible solution was to cut the supplied Mini-DIN6 cable open, locate the offending wire and cut it.  Not a solution I relish doing.  The other was to try and fix the UDRC-II.

Discussing this on the list, it was suggested by Bryan Hoyer that I use a 4.7k pull-up resistor on the offending pin to 3.3V.  He provided a diagram that indicated where to find the needed signals to tap into.

With that information, I performed the following modification.  A 1206 4.7k resistor is tacked onto the squelch status pin, and a small wire run from there to the 3.3V pin on a spare header.

UDRC-II modification for Yaesu FT-897D

UDRC-II modification for Yaesu FT-897D

I’m at two minds whether this should be a diode instead, just in case a radio asserts +12V on this line, I don’t want +12V frying the SoC in the Raspberry Pi.  On the other hand, this is working, it isn’t “broke”.

Doing the above fixed the squelch drive issue and now I’m able to transmit and receive using the UDRC-II.  Many thanks to Bryan Hoyer for pointing this modification out.