Servo Driver 1
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.
Parts
| No | Value | Part No | Off | Unit £ | Total £ |
|---|---|---|---|---|---|
| IC1 | LM555 | 82-0336 | 1 | 0.20 | 0.20 |
| 8 pin socket | 22-0150 | 1 | 0.06 | 0.06 | |
| C1 | 470nF | 10-2224 | 1 | 0.14 | 0.14 |
| C2 | 100nF | 10-2216 | 1 | 0.08 | 0.08 |
| C3 | 100nF | 10-2216 | 1 | 0.08 | 0.08 |
| C4 | 2200nF | 10-2200 | 1 | 0.36 | 0.36 |
| R1 | 2k7 | 63-2407 | 1 | 0.27 | 0.27 |
| R2 | 68K | 63-2423 | 1 | 0.27 | 0.27 |
| R3 | 100R | 63-2402 | 1 | 0.27 | 0.27 |
| P1 | 2K5 LIN pot | 68-1274 | 1 | 1.78 | 1.78 |
| Knob 0.25mm | 32-0330 | 1 | 0.44 | 0.44 | |
| D1 | IN4148 | 47-3416 | 1 | 0.01 | 0.01 |
| SW1 | DPDT slide | 76-0100 | 1 | 0.16 | 0.16 |
| B1 | AA Batteries 4pk | 18-3299 | 1 | 2.99 | 2.99 |
| B2 | AA Holder | 18-0121 | 4 | 0.15 | 0.60 |
| Case | ABS 13x7x4.4 | 30-3362 | 1 | 1.78 | 1.78 |
| Total | 9.49 | ||||
| PCB | Stripboard 6.4x9.5 | 34-0505 | 1 | 0.72 | 0.72* |
| Wire | 11x2m 7/0.2 | 01-0180 | 1 | 1.44 | 1.44* |
| Lead | Futaba M/F | 250mm | 1 | 1.00 | 1.00* |
| Total | 12.65 | ||||
| Delivery | 5.69 | ||||
Servo Driver 2
Go to Murry State University for full description and original circuit diagram.
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.
Parts
| No | Value | Part No | Off | Unit £ | Total £ |
|---|---|---|---|---|---|
| IC1 | LM555 | 82-0336 | 1 | 0.20 | 0.20 |
| 8 pin socket | 22-0150 | 1 | 0.06 | 0.06 | |
| C1 | 330nF Tantalum | 11-1060 | 1 | 0.08 | 0.08 |
| C2 | 100nF | 10-2216 | 1 | 0.08 | 0.08 |
| C3 | 220nF | 10-2220 | 1 | 0.08 | 0.08 |
| R1 | 220R | 63-2395 | 1 | 0.27 | 0.27 |
| R2 | 68K | 63-2423 | 1 | 0.27 | 0.27 |
| P1 | 5K0 LIN pot | 68-1276 | 1 | 4.89 | 4.89 |
| Knob 0.25mm | 32-0330 | 1 | 0.44 | 0.44 | |
| D1 | IN4148 | 47-3416 | 1 | 0.01 | 0.01 |
| SW1 | DPDT slide | 76-0100 | 1 | 0.16 | 0.16 |
| B1 | AA Batteries 4pk | 18-3299 | 1 | 2.99 | 2.99 |
| B2 | AA Holder | 18-0121 | 4 | 0.15 | 0.60 |
| Case | ABS 13x7x4.4 | 30-3362 | 1 | 1.78 | 1.78 |
| Total | 11.91 | ||||
| PCB | Stripboard 6.4x9.5 | 34-0505 | 1 | 0.72 | 0.72* |
| Wire | 11x2m 7/0.2 | 01-0180 | 1 | 1.44 | 1.44* |
| Lead | Futaba M/F | 250mm | 1 | 1.00 | 1.00* |
| Total | 15.07 | ||||
| Delivery | 5.69 | ||||
Servo Driver 3
This circuit behaved oddly and is of no practical use.
Go to Alan Franzman’site for full description and original circuit diagram.