Point C, the voltage measured from ground should rise to
approximately 6V and fall for every sound pulse; there
should be no AC component.
If all is okay to this point, in DC mode check the
operation of the FFs using Table 1. Next, check the gates
of the MOSFETs (Q1 and Q2) to see that they are
receiving switching pulses. If not, they may be damaged.
Are LED1 and LED2 in the correct orientation? By now,
you should have discovered the area of the problem and a
way to correct it.
Using the Train Voice
Set the jumpers (SW1A, B, C) for your locomotive’s
electrical power system (AC or DC mode) and connect
the wiring for the train power appropriately as shown in
Figure 5. Set the speed control of the train’s transformer
or power unit for the desired speed.
For AC mode, ensure that the locomotive’s
sequencing mechanism (E-unit) is not locked out with its
lockout lever or switch.
In DC mode, the power connections are reversed
when the locomotive is sequenced to “reverse.” The
train’s power unit common output is transferred to the
“hot” rail and vice versa. This may not work for some
arrangements. A solution is to provide both positive (+)
and negative (–) power for the loco and use the relay
arrangement in Figure 11.
You will need some practice. For AC mode, LED1 will
help by showing the sound pulses used to interrupt the
power. For DC mode, LED1 and LED2 will show the
switching sequence (Figure 6 and Table 1). You may need
to adjust the GAIN and DECAY. Here are a few examples
(also see Table 2):
Suppose that the train is stopped and you know that it
was in reverse before it stopped. To command it to go
forward, you can simply say “go” or “forward” if you make
“forward” one continuous sound (indicated here by
underlining). In other words, you are switching from state
Sr to F. By “one continuous sound,” I mean that only one
pulse is produced.
Now you can say “halt” or “stop” to stop the train,
going from F to Sf. Next, you can say “back” or “reverse”
or “back up” (making “reverse” or “back up” one
continuous sound) to go from Sf to R. The DECAY
adjustment is what allows “back up” to act as one
continuous sound and produce one pulse.
As a final example, if the train is stopped after going
forward (Sf) and you want to go forward again (F), you will
need three pulses. So, you could say “now ... go ...
forward” or “go ... for ... ward,” splitting the word
“forward” to produce two pulses.
Be careful when saying “stop” or “up” that the final
“p” isn’t a separate sound producing an additional pulse.
Try to cut it off or speak across the mike rather than into
it. On the other hand, sometimes you may want “stop” to
be two separate sounds.
With a little practice, you can make one word cause
two pulses (by separating sounds) or two words make one
pulse (by running sounds together). The length of the
pulses is not important, except that if they are too long,
onlookers will become suspicious (for example, for the
intermediate stop between forward and reverse). Again,
this depends on the DECAY adjustment.
Other languages will work as well: French (avant,
arrière, arrêt ...); Spanish (vaya, deje de, atras ...); German
(vorwärts, halt, zuruck ...); etc., or make up your own
language or set of commands.
With some practice, you will get the hang of it. Have
1. I have tried several microphones and they all worked, including: Goldsun EC928-602 (Jameco 2099622, discontinued),
Jameco Valuepro EM-99-R (Jameco 320179), Jameco Valuepro AMF-097A40-NB1-LF (Jameco 1950948), Kobitone 254-ECM970-
RO (Mouser 254-ECM970-RO), DB Unlimited MO064404-1 (Mouser 497-MO064404-1) (small diam), Emkay 3340 LN100, CZN-
15E, and two mystery microphones.
Different microphones may require different amounts of op-amp gain (R7). Observe the polarity when wiring the microphone.
2. If Q1and Q2 are MOSFETs, anything from 0Ω to 47 kΩ should work for R1; R2 (and C8) may be altered, but R2 x C8 should
be approximately 0.05-0.1 Ω-farad (approximately 0.05-0.1 second time constant). If Q1 and Q2 are BJTs, use between 3. 3 kΩ
and 4. 7 kΩ for both R1 and R2.
3. The preferred op-amp is LF411ACN (Mouser LF411ACN/NOPB; Jameco 23018) which has low input offset voltage. However, if
you have them on hand, you could try LF356N or TL081B if the op-amp output voltage (pin 6, Point A) measures within a few
tenths (+ or –) of the midpoint voltage (Point D).
4. I have tried many other optocouplers, some new and some from my recycle bin including: Toshiba TLP621-2 (dual eight-pin);
Sharp PC123, PC817, and S21MT1; Vishay TCET1102 and TCET1109; and NEC NEC2501, NEC2561, and NEC2561-A, all of which
worked. A single dual anti-parallel-input optocoupler could be used (for example, type FOD814A).
5. Check that the contact current rating of the relays is adequate for your locomotive. If using RTD14012, note that there are
two pins for the pole and two pins for each contact (NO and NC).
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