In the world of electric vehicles (EVs) and electric bikes (ebikes), throttles are essential components that control the speed of the motor. But how exactly do these throttles work? In this blog post, we'll delve into the inner workings of e-bike and EV throttles, explaining the different types and how they function.
Types of Throttles:
There are two main types of throttles:
Hall sensor throttles: These are the most common type of throttle, and they use a magnet and a Hall sensor to measure the position of the throttle grip. As the grip is rotated, the magnet moves closer or further away from the sensor, which changes the voltage output. This voltage signal is then sent to the controller, which determines the amount of power to send to the motor.
Resistive throttles (also known as Potentiometer throttles): These throttles use a simple resistor to control the voltage output. As the grip is rotated, the resistance changes, which in turn changes the voltage output. While less common than Hall sensor throttles, they are still found on some ebikes and EVs.
How Hall Sensor Throttles Work:
- Magnet and Hall sensor: The throttle grip contains a magnet and a Hall sensor. As the grip is rotated, the magnet moves closer or further away from the sensor.
- Voltage scaling: The Hall sensor detects the position of the magnet and sends a corresponding voltage signal to the controller. This signal typically ranges from 0.8 to 5 volts, with 0.8 volts representing no input and 5 volts representing full throttle.
- Controller interpretation: The controller receives the voltage signal from the throttle and interprets it as a command for motor speed. The higher the voltage, the faster the motor will spin.
- Noise elimination: Some throttles have a built-in mechanism to eliminate noise from the voltage signal. This is done by clipping off a small portion of the voltage range, typically around 1 volt. This helps to prevent sudden bursts of speed or unintended acceleration.
How Resistive Throttles Work:
- Variable Resistor: The core of a resistive throttle is a variable resistor (often called a potentiometer). This resistor has a track-like element with a "wiper" that moves along the track.
- Changing Resistance: As the throttle grip is rotated, the wiper's position on the resistor track changes. This alters the effective resistance between two points on the resistor.
- Voltage Divider: The resistive throttle acts as a voltage divider. The controller supplies a fixed voltage (often 5 volts) across the resistor. As the wiper moves, the voltage output taken from the wiper changes proportionally to its position (and the resulting resistance).
- Controller Interpretation: Similar to Hall sensor throttles, the controller interprets this changing voltage signal. Higher voltage commands a faster motor speed, and lower voltage instructs the controller to reduce the motor's speed.
How controllers read throttle signals:
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Calibration: Most controllers will automatically perform a calibration routine to learn the minimum and maximum voltage output by the throttle. This calibration allows the controller to understand the maximum voltage provided which for example it could be 3.8v or 4.2v ect. This is interpreted by the controller as "full throttle" or max power. On the other hand the lowest voltage provided or "zero throttle" reading, which in the case of hall sensor throttles most commonly being 0.8v, is understood as "zero throttle" and therefore no power is given to from the controller to the motor.
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Scaling: Once the controller has calibrated the throttle signal, it will scale the voltage input to a range that the motor controller can understand. This is typically a range of 0-5 volts, but it can vary depending on the specific controller.
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Resolution: The resolution of the throttle signal, which is determined by the number of steps between the minimum and maximum voltage, can affect the smoothness of the power delivery. A higher resolution throttle will provide more precise control over the motor, while a lower resolution throttle may result in a noticeable "stepped" power delivery.
How to determine which type of electric throttle you have:
A resistive throttle will have a voltage range from around 0-5v, always starting at 0v.
A hall sensor throttle will have a voltage range around 0.8-4.2v, always starting higher than 0v due to the always powered on (active) state of hall sensors.
Both hall sensor and resistive throttle types have three connection wires, most commonly white/red/black or green/red/black. When connected to a 5vdc power source, you can take a voltage reading from the signal wire.
Additional Features:
Some throttles may have additional features, such as:
- Voltmeter: This allows you to see the battery voltage in real-time.
- Switch: This allows you to turn the throttle on or off.
- Multiple wires: Some throttles have multiple wires for connecting to the controller and other components.
Understanding throttles is essential for anyone who rides an ebike or EV. By knowing how they work, you can troubleshoot problems and get the most out of your ride.
I hope this blog post has been helpful! If you have any questions, please feel free to leave a comment below.