IOCAN

# PWM Output

## Overview

A **PWM Output** drives a hardware pin with a pulse-width-modulated signal. It is

the most common output type, used to control solenoids, proportional valves,

lamps/LEDs, fans, and other actuators where the average power is set by the duty

cycle.

It runs in one of two modes:

- **PWM mode** — you command a **duty cycle**; the pin switches at the configured

  frequency.

- **Current mode** — the output regulates to a commanded **current** (closed-loop),

  which is what most proportional solenoids need for repeatable behaviour.

## Prerequisites & hardware

- Wire the actuator between the output pin and its return per the controller pinout;

  observe the channel's current rating.

- Fit a **flyback/freewheel path** for inductive loads (solenoids, relays) if the

  channel does not provide one.

- For current-controlled solenoids, use **Current mode** and set the

  **current limit** to the actuator's rating.

## Add it in the app

1. Add a new output and choose **PWM Output** as the type.

2. Select the **pin** and give it an **alias** (e.g. `Line Pressure Solenoid`).

3. Choose **Mode**, set the **frequency**, and configure **peak & hold** if the

   actuator needs it.

4. Drive the output from a map/driver that supplies the duty or current command.

## Settings reference

> Schema: `config/PwmConfiguration.proto`.

| Setting | Meaning | Unit | Range / values | Notes |

|---|---|---|---|---|

| **Mode** | Control strategy | — | `PWM`, `Current` | `PWM` = command duty cycle; `Current` = closed-loop current regulation. |

| **Frequency** | PWM switching frequency | Hz | 100 – 4000 | Higher = quieter/smoother; match the actuator's recommended frequency. |

| **Invert** | Inverts the output polarity / duty | — | on / off | Use when the load is wired active-low or logic is reversed. |

| **Current limit** | Maximum output current | mA | uint32 | Protects the actuator and driver; used as the regulation target ceiling in Current mode. |

| **Peak & hold** | Enables a peak-then-hold drive profile | — | on / off | Pull a solenoid in at high current, then hold it with less — saves power/heat. |

| **Peak value** | Current/duty during the peak phase | mA or % | sint32 | Applied for the peak time at engage. |

| **Peak time** | Duration of the peak phase | ms | sint32 | How long the peak value is applied before dropping to hold. |

| **Hold value** | Current/duty during the hold phase | mA or % | sint32 | Steady-state level once engaged. |

| **Proportional hold** | Scales the hold level proportionally | — | on / off | Hold tracks the command rather than a fixed level. |

## Common settings

PWM Output also uses the shared settings — alias and pin. See [Common IO Settings](Common_IO_Settings).

## Example — peak-and-hold shift solenoid

1. Type **PWM Output**, alias `Shift Solenoid A`, on the solenoid's pin.

2. **Mode = Current**, **Current limit** = solenoid rating.

3. **Peak & hold on**: Peak value = high pull-in current, **Peak time** ≈ 30–60 ms,

   **Hold value** = lower steady current.

4. **Frequency** per the solenoid data sheet (commonly 1–2 kHz).

5. Command it from the shift logic/map.

## Troubleshooting

- **Actuator buzzes / audible whine:** raise the **frequency** above the audible

  range or to the actuator's recommended value.

- **Solenoid won't pull in but holds weakly / vice-versa:** revisit **peak value**

  and **peak time**.

- **Output runs backwards / always on:** check **Invert**.

- **Overheats or trips:** check the **current limit** and that hold current isn't

  set too high.

## Related

- [Analog Output](Analog_Output) — for an analog voltage instead of PWM.

- [Tacho Output](Tacho_Output) — generated tacho/frequency signal.