Servo Driver

Servo Driver 1

Tony van Roon's servo pulser

Go to Tony van Roon’s site for full description and original circuit diagram.
 
This circuit drove the Futaba 3003 servo over the same 80 degree angle as did the Tx/Rx.
 
The stared * items have been changed/added as the original values are unobtainable in the UK.
The original R1 and R2 would give a resistance of 2K7 to 5k4 for a pulse band of 1mS to 2mS. The 2K5 pot plus the added 100R resistor now gives a range of 2K8 to 5K3. This shorter range should not be a problem as the Servo's pulse band is 1.1 to 1.9mS.
The two capacitors in series give a value of 390nF using 1/C = 1/C1 + 1/C2 ....
 
Note the correct direction of D1. The black ring on the diode is the bar on the symbol.
The crosses on IC 555 show the positions where the copper on the stripboard has to be cut between pins 1/8 2/6 3/5 4/5. Hand use a twist drill to remove the copper. The direction to fit IC 555 is shown by a dot or semi-circle.
 
The scale 1 to 2mS is the full travel of the pot.

PCB layout for pulse driver 1
photo case, pcb and scale

Parts

No Value Part No OffUnit £Total £
IC1 LM555 82-0336 10.200.20
  8 pin socket22-0150 10.060.06
C1 470nF 10-2224 1 0.140.14
C2 100nF 10-2216 1 0.080.08
C3 100nF 10-2216 1 0.080.08
C4 2200nF 10-2200 1 0.360.36
R1 2k7 63-2407 10.270.27
R2 68K 63-2423 10.270.27
R3 100R 63-2402 10.270.27
P1 2K5 LIN pot 68-1274 11.781.78
  Knob 0.25mm 32-0330 10.440.44
D1 IN4148 47-3416 10.010.01
SW1 DPDT slide 76-0100 10.160.16
B1 AA Batteries 4pk18-3299 12.992.99
B2 AA Holder 18-0121 40.150.60
Case ABS 13x7x4.430-3362 11.781.78
  Total9.49
PCB Stripboard 6.4x9.5 34-0505 10.720.72*
Wire 11x2m 7/0.2 01-0180 11.441.44*
Lead Futaba M/F 250mm 11.001.00*
  Total12.65
  Delivery5.69

 

Servo Driver 2

Go to Murry State University for full description and original circuit diagram.

R. Andrew Batts's servo Driver

This circuit drove the Futaba 3003 servo over the full 200 degrees.
 
On the clockwise end the variable resistor could be turned beyond the servo limit. I tried replacing the 5K pot with 4.7K then adding a 1K5 resistor in series but these made things worse.
I turned the pot until it reached the servo limit, unsoldered it and found its resistence 3K4. I then tried a 12K resistor in parallel to bring the 4K7 pot down to 3K4 but the servo went beserk.
 
The 0.6 and 2.4mS points on the scale were found by rotating the pot until the Futaba servo 3003 stopped turning. This was not the full travel of the pot. It was interesting that some servos worked beyond these values even down to 0nS.

PCB layout for servo driver 3

 

Parts

No Value Part No OffUnit £Total £
IC1 LM555 82-0336 10.200.20
  8 pin socket22-0150 10.060.06
C1 330nF Tantalum 11-1060 1 0.080.08
C2 100nF 10-2216 1 0.080.08
C3 220nF 10-2220 1 0.080.08
R1 220R 63-2395 10.270.27
R2 68K 63-2423 10.270.27
P1 5K0 LIN pot 68-1276 14.894.89
  Knob 0.25mm 32-0330 10.440.44
D1 IN4148 47-3416 10.010.01
SW1 DPDT slide 76-0100 10.160.16
B1 AA Batteries 4pk18-3299 12.992.99
B2 AA Holder 18-0121 40.150.60
Case ABS 13x7x4.430-3362 11.781.78
  Total11.91
PCB Stripboard 6.4x9.5 34-0505 10.720.72*
Wire 11x2m 7/0.2 01-0180 11.441.44*
Lead Futaba M/F 250mm 11.001.00*
  Total15.07
  Delivery5.69

 

Servo Driver 3

Alan Franzman's servo driver

This circuit behaved oddly and is of no practical use.
 
Go to Alan Franzman’site for full description and original circuit diagram.