Sunday, September 15, 2013

How I added MyLocoSound to a battery powered steam loco

The latest version of the MyLocoSound card was bought from Peter Spoerer. This version incorporates 'coasting' which senses when the loco is accelerating and decelerating and adjusts the volume of the chuff accordingly.

A wire was soldered to pad 6 of the Deltang rx61-22 receiver/controller. This pad is controlled by the bind button on the Tx22 transmitter and will be used to operate the sound card's whistle.

 Because the sound card needs the input for the whistle to be connected to ground (-ve) to trigger the sound and the output from the receiver/controller is 3v (+ve), I constructed a simple transistor switch using the guidance provided on the Deltang website (see How I constructed a simple transistor switch)

A small 'laptop' speaker (provided by Peter Spoerer) was fixed to the cab roof with a double-sided sticky pad and the wires fed through into the firebox.

The internal bracing between the firebox and the boiler was pared down to accommodate the sound card (the blue/purple wires connect to the speaker and the red/black wires are the switched feed from the battery).

The wires were then connected to the terminal block on the sound card. From top to bottom:
  • speaker wires (x2)
  • spare
  • whistle trigger (from the transistor switch)
  • negative supply (and -ve lead to controller/receiver and to transistor switch)
  • positive supply (and +ve lead to the controller/receiver)

Into the terminal block at the other end of the card went the leads to the motor and the leads from the controller/receiver for the motor and finally the two jumpers were removed from the sound card (for 'other' PWM controller settings).

This wiring diagram should hopefully make the setting-up a little more understandable (click to enlarge):

The chassis was then mounted on to a rolling road and the loco turned on so the sound board could be callibrated using the adjuster pots along the top of the board. From left to right:
  • Whistle volume
  • Whistle tone (from tiny peep to throaty roar)
  • Chuff volume
  • Spare
  • Chuff speed (set to match the wheel speed at max)
  • Chuff start (set to start the chuff when the wheels begin to move)

Something I discovered is (of course) that the start setting and the upper speed differs when the loco is under load and so eventually I decided to find the happy medium between unloaded and loaded settings.  The receiver/controller, switch and board were then slotted into the space for them between the firebox and the boiler ........

 ...... and the loco was taken outside for extensive test-running.

How I constructed a simple transistor switch

The output pads from the Deltang receiver/controllers (Rx60-22 and Rx61-22) are restricted to 3 volts and can only handle the load of one LED. To enable each pad to switch higher voltage/current devices a simple transistor switch is needed. The wiring circuit for this switch is provided on the Deltang website and the three components required cost less than £2.00 in total.

I bought the electronic items needed for each switch from
  • a IRF3706 N-Channel Mosfet transistor
  • a 100 ohm resistor
  • a 10k ohm transistor
The two resistors (100R and 10k) were soldered together and a wire attached to the other end of the 10k resistor.

A (yellow) wire was soldered to the middle leg of the MOSFET and the resistors attached to the other two legs (with the 100R resistor leading to the left leg).

A piece of heatshrink sleeving was slipped over the middle lead ........

...... and a (purple wire soldered to the 100R resistor and another piece of heatshrink slipped over them.

After testing, the whole assembly was wrapped in heatshrink as the mounting bracket of the MOSFET is live and so needs insulating.

The purple wire was soldered to the lead from pad on the receiver/controller, the black wire was soldered to the negative lead from the battery and the yellow lead connected to the device needing to be remotely switched (eg a cluster of LEDs, the supply to a sound card, the whistle input on a sound card, etc.)

Sunday, September 01, 2013

Adding a sound module to a battery loco

After some deliberation, I decided it was time I experimented with adding sound to at least one of my battery locos. As she was the loco which was on the workbench at that particular time, I decided to investigate options for adding sound to the IP Engineering 'Jessie' kit which I had recently completed (see How I constructed an IP Engineering diesel kit).

After exploring various alternatives, I contacted Peter Spoerer by email and he suggested I gave him a ring to hear his latest narrow gauge diesel sound module. After a few minutes I was convinced that his unit was just what I needed for 'Wynford' as 'Jessie' had now been re--christened.

A couple of days later, a small parcel arrived containing the bits I needed - the sound module, a radio controlled switch and a small loudspeaker. Although the kit comes with a loudspeaker, I opted for a smaller 'laptop' unit in its own housing which I felt would be easier to fix into place.

The first thing I did was to fix the speaker to the inside of the cab roof with a double-sided sticky pad.

Once the problem of siting the speaker had been solved, I ran the wire through to the front part of the loco where I was hoping there would be sufficient space to add the electronics alongside the NiMh batteries, the Brian Jones Mac Five speed controller and the Deltang receiver.

The wiring for the unit was extremely straightforward and very logical. Two wires (red and black) were connected to the battery feed for the controller, to provide power the module, another two wires were connected to the feed for the motor (yellow and blue) to sense the speed of the loco. Two wires (red and black) were connected to the speaker and another two wires (white) were connected to the radio controlled switch which is used to control the horn and to start-up and stop the sound unit. From the switch a plug is connected to one of the channels of the receiver (in my case channel 3). There is a volume control on the module - I set mine to about 85% of full volume.

After testing the unit (it worked first time!!), the next job was to try and cram everything into the space left under the bonnet of the loco. I neatly coiled the wires and then held everything in place with a few strips of masking tape.

The wires from the controller were plugged into the leads for the loco's headlight and the bonnet was then carefully screwed into place.

 This took a couple of tries but eventually, the loco was back on the rails for some trialling.

 The start-up and wind-down sounds of the engine are excellent. The transition from tick-over to running sound is dictated by the unit which presumably senses the input to the motor and moves in a predetermined way from one to the other. As the sounds are real recordings of a diesel loco, the sound is not directly linked to the speed of the loco, but once under way the engine noise is quite appropriate for a loco which generally tends to run fairly slowly.

As you can hear from the video, the sound module is extremely effective and to my mind well worth the investment. I am now more determined to add sound to my other battery locos - as soon as funds permit!