ToolkitRC ST8 Servo-Tester

ToolkitRC ST8 is a multifunction servo tester suitable for testing, adjusting, and load testing servos in the workshop. Unlike common simple testers, it offers 4 independent programmable channels and measures current draw, response speed with 1ms accuracy, and the number of cycles performed for each servo. The main output provides up to 28V and can handle a servo load of up to 100W, so it can also handle large high-voltage servos. Everything is shown on a color 2.4" TFT display with a resolution of 320x240 pixels.

The tester is powered through the rear input with 7-28V (max. 10A), for example from a flight battery or a mains power supply, which is not included. Output voltage is selected in settings in steps of off, 5, 6, 7.4, 8.4, 12, 14, 15, 16, 18, 24 and 28V. In the 5-8.4V range, the main output and signal ports S1-S4 share the same voltage. At 12-28V, high voltage goes only to the main output and the signal ports remain at 5V, so the large servo is powered from the main output and receives signal from the signal port. With the main output turned off, the signal ports provide 5V with a load of up to 15W, and if the servo exceeds this, the tester prompts you to turn on the main output. The tester continuously monitors input voltage and the motherboard temperature, and turns off the main output if the voltage drops below the set threshold or if the safe temperature is exceeded.

The main screen displays channels S1-S4 as color-coded columns with pulse width. In the center, the current waveform of all four outputs is drawn, and the bottom bar shows the maximum current, speed, and cycle count of each channel in real time. In pause mode, the signal stops at a fixed value and the rotary wheel can be used to browse the stored current curve, making it easy to find current spikes.

Each channel can take its signal from a different source. The P1 rotary knob controls pulse width in the 1000-2000µs range and is locked by pressing it. The external S5 input accepts PWM, PPM (8 channels), and SBUS (16 channels), so the tester transfers the receiver signal to the servo while also displaying the received values. The internal generator offers a linear mode that smoothly sweeps the range with a 1-10µs step and 1-10ms speed, and a phase mode that jumps between two or three positions (PS, PC, PE) every 1 second and is used to measure response speed. Both modes are intended for long-term load tests ("aging") – they count cycles and stop automatically after reaching the set count. Positions PS, PC and PE can also be triggered by the display buttons, while the tester measures the time it takes for the servo to reach the position. Channels 2-4 can also copy channel S1. The PWM output range is set between 100-2900µs with 1µs accuracy and a period of 1-30ms (33-1000Hz), covering both the common 50Hz signal and high refresh rates.

Control is handled by a rotary wheel with OK button function, an Exit button, and the P1 knob. Settings allow you to change display brightness (1-10), buzzer, light or dark theme, calibrate the P1 knob, reset the cycle counter, or restore factory settings. The menu is in English and Chinese, and additional languages can be added via an update. Firmware is updated via microUSB – after connecting to a computer, the tester appears as a USB flash drive, where you only need to copy the update file. The tester measures 99x68x26 mm and weighs 120g.

Important notice: When connecting power, polarity must be observed. Signal ports S1-S4 and S4 Ext. are intended for lower currents and a voltage of up to 8.4V – servos with higher current draw or higher voltage must be powered from the main output, otherwise internal circuits of the tester may be damaged. We recommend not leaving the tester unattended during operation and disconnecting it from power after use.