| 23KG·CM STALL | 0.100S/60° NO-LOAD | 8.4V RATED |
| 65G WEIGHT | StainlessGEARTRAIN | 360°TRAVELCustomizable |
Overview
The S8020D is a 23 kg·cm coreless digital servo in a 20 × 40 × 34.9 mm case, 65 g. It is the thinner alternative to the brushless models in the same footprint: 34.9 mm deep instead of 38–40, which is what matters when the servo sits under a narrow fuselage or inside a tight frame.
Coreless motor, stainless steel geartrain on two ball bearings, 25T-φ5.94 mm spline and a POM horn. Mechanical limit 210°, dead band 1 µs, and the pulse window is the standard 800–2200 µs.
This page covers the TTL build: the same mechanics, commanded over a serial bus so several servos can share one signal line and be addressed individually. Useful when the actuator count outgrows the PWM channels available.
Performance at each supply voltage
| Supply | No-load speed | Peak stall torque | Idle current | Stall current |
|---|---|---|---|---|
| 6.0 V | 0.140 s/60° (429 °/s) | 17 kg·cm (1.67 N·m / 236 oz·in) | 300 mA | 2.8 A |
| 7.4 V | 0.120 s/60° (500 °/s) | 20 kg·cm (1.96 N·m / 278 oz·in) | 350 mA | 3.0 A |
| 8.4 V | 0.100 s/60° (600 °/s) | 23 kg·cm (2.26 N·m / 319 oz·in) | 420 mA | 3.5 A |
Control specification
| Item | Specification |
|---|---|
| Command signal | TTL serial |
| Amplifier | Digital controller |
| Dead band | 1 µs |
| Rotating direction | CCW (1000–2000 µs) |
| Travel | 360°, customizable |
Mechanical specification
| Item | Specification | Item | Specification |
|---|---|---|---|
| Dimensions | 20 × 40 × 34.9 mm | Case material | Aluminium, CNC |
| Weight | 65 g | Geartrain | Stainless steel |
| Bearings | 2 × ball bearing | Motor | Coreless |
| Output spline | 25T-φ5.94 mm | Horn | Plastic, POM |
| Lead / connector | 300 mm, 3-wire | Mechanical limit | 210° |
| Operating temperature | −15 °C to 65 °C | Storage temperature | −20 °C to 70 °C |
| Ingress protection | Splash resistant (customizable) | Travel | 360°, customizable |
What’s in the box
- 1 × XQ-S8020TTL servo
- 1 × POM horn set
- 1 × mounting screw pack
Optional: metal horn, sold separately.
How to size it
Torque tracks the rail: 17 kg·cm at 6.0 V, 20 at 7.4 V, 23 at 8.4 V, at 0.14, 0.12 and 0.10 s/60°. On a 2S pack under load, plan on 20.
Stall current is only 3.5 A at 8.4 V against 420 mA no-load. A coreless motor has no iron in the rotor, so it accelerates faster and draws less at stall than a cored motor of the same torque — four of these on a 15 A BEC is a comfortable margin.
FAQ
Is it 22 kg·cm or 23?
23 kg·cm is the measured peak at 8.4 V on the inspection sheet. 22 is the nominal figure carried in the product name. The table above lists the measured values for all three rails.
Coreless or brushless?
Coreless. It is lighter and thinner than the brushless models in this footprint (65 g, 34.9 mm) and has lower stall current, but the brushes remain a wear item. For continuous duty at high torque, the brushless BLS8135D is the longer-lived choice.
Is the pulse width table valid for this unit?
No. The microsecond window printed on the inspection sheet belongs to the PWM build of the same servo. This unit is commanded over the serial bus — ask for the command set and register map before writing firmware.
How many can share one bus?
The limit is the address space and the current budget of the shared supply, not the signal pair. Keep the bus ground common with the power ground at a single point.
Other interfaces
Downloads
- XQ-S8020TTL inspection specification (PDF, 717 KB)
Torque, speed and current at each supply voltage, mechanical data, control specification, mounting dimensions. - 2D dimension drawing (image)
Mounting hole positions, case depth and overall height; the same drawing is inside the datasheet.
