General Stuff(tm)

[stephen_usher]

Tried it on another loco, without resistor or the 1uF capacitor. Seemed to work OK for a while with a better speed response, but then the chip went POP!

Oh well, it's only £18 and I was expecting to pop one of them at some point.

[stephen_usher]

Well, it looks like that DCC decoder must have been faulty to begin with as it didn't behave the same way as its replacements.

Anyway, I've finished redesigning the Hornby ringfield motor DCC socket PCB using the knowledge from the first version.
I'm not sure if/when I'll get these built as I can work around the issues with the original design by a bit of very careful soldering for the capacitor and installing the twin, parallel 10 ohm resistors into one of the motor wires.

Still, the design's complete and if I chose to build them (if I wanted to sell them) I could.

Due to the DCC decoder board outputting pulsed 17V to the motor and the Hornby ringfield motor windings being ~13 ohms there's a possibility of the motor drawing more than the maximum 1 amp that the board supports. That's why I've added the twin 10 ohm resistors in parallel. This brings the total resistance up to 18 ohms, meaning that the maximum power draw will be below 1 amp even if the motor stalls completely. Using two 10 ohm resistors spreads the current and potential thermal load. With them being surface mount (2010 packages) I can also add a heatsink if necessary.

[stephen_usher]

Hmm... I'm wondering about lighting now.

I have a loco LED light unit which shows one set of colours in one direction and another when the voltage is reversed.

However, the DCC decoder has two open drain collectors for the two directional light functions, the other source of power is the AC power from the rails. This is designed so that you can take the rail voltage, put it through a diode and then through either a bulb or the anode of an LED and thence to the control connection on the decoder. For one direction it turns on the transistor on one connection and in the other the other.

I'm trying to think of a way of turning this pair of on/off open drain switches + AC into bi-directional DC and failing. Anyone have any ideas?

[stephen_usher]

All the model railway stuff now packed away again and the Falcon, Memotech etc. brought back out of storage to get ready for next weekend's show in Cambridge.

[stephen_usher]

A working NetUSBee on the Falcon made copying demos and Ace Tracker files onto the machine a doddle and quick.

A pity that most of the demos used graphics modes that the VGA monitor I'm using at the moment can't handle (the "Sun" rebadged NEC may do better). One did say effectively, "VGA... no play."

[stephen_usher]

Arrived in Cambridge for the weekend retro event at the Centre for Computing History.

I have to wait until 5pm before I can go over there and start setting up.

[Steve]

A working NetUSBee on the Falcon made copying demos and Ace Tracker files onto the machine a doddle and quick.

A pity that most of the demos used graphics modes that the VGA monitor I'm using at the moment can't handle (the "Sun" rebadged NEC may do better). One did say effectively, "VGA... no play."

Yeah lots of demos only run in RGB mode. I haven't been able to run them because I've never had an RGB capable monitor. I did plug my Falcon into Composite to a TV once though just so I could watch 'hmmmm' demo.

[stephen_usher]

Yeah lots of demos only run in RGB mode. I haven't been able to run them because I've never had an RGB capable monitor. I did plug my Falcon into Composite to a TV once though just so I could watch 'hmmmm' demo.

Even if they do run in VGA mode they often require 100Hz refresh rates, which few VGA monitors can handle.

[stephen_usher]

Well the first day of Retrofest 2022 is over and I'm dog tired.

Here are some photos:

IMG_2838.jpeg

IMG_2839.jpeg

IMG_2840.jpeg

IMG_2842.jpeg

IMG_2843.jpeg

Of course, for the first time ever the QL managed to corrupt a floppy disk image on the Gotek. Still, I have another copy of the image at home so it's OK and things going wrong when on display and never at any other time is perfectly normal.

[stephen_usher]

And it's over for another year.

I'm back in the hotel, shattered.

I drive home tomorrow morning and the move a lot of the stuff straight into the storage unit.