Synthesis Technology MOTM-850, Руководство пользователя

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SYNTHESIS TECHNOLOGY PAGE 13
MOTM-850 ASSEMBLY 10/25/01
WWW.SYNTHTECH.COM
The op amp and comparator are powered off se-12V supplies by U2 and U3. This is
done for several reasons. First, it provides a load-isolated voltage reference for the OFFSET
and GATE pots (the pedal doesn’t need this). Second, it isolates current spikes from the
+15V line as the LED switches on and off.
The LM311 output is open-collector, so R3 provides the pullup.
The GATE signal can be selected to be positive-true (VTRIG) or shorting-to-ground
(STRIG). Moog uses STRIG, everybody else uses VTRIG. Jumper JP2 selects which type is
outputted to the jack. The output of the comparator is a VTRIG (rises to +12V when the
comparator trips), and a simple transistor inverter Q1/R1/R8 provides STRIG. Q1 also is a
‘free’ way to drive the GATE LED D1, since we are turning on the LED by shorting it’s
cathode to ground (did I mention how clever we are?).
INTERFACING TO THE ROLAND EV-5
The EV-5 pedal has 2 pots wired in series. The pedal mechanism pot is a 10K +-20% and a
separate ‘offset trimmer’ pot of 50K. See Figure 1.
Assuming the trimmer pot is at dial position ‘0’ (normal operation), the circuit is simple.
The jumper JP3 is set to feed +15V through R18 (16K5). The output is from the wiper and
is given by the equation:
Vout = 15 * (Rdown)/(Rdown+16500 +10000)
Where 16500 is the value of R18 and 10000 is the value of the pedal pot. Rdown is the
fractional resistance of the 10K pot as you press down.
R O L A N D E V -5 P E D A L
O F F SE T
T R IM
C O N T R O L
50K
10
1
D W N
U P
P E D A L
10K