# How Does the RoboRoach Backpack Work?

**URL:** <https://forum.backyardbrains.com/t/how-does-the-roboroach-backpack-work/82>\
**Category:** Equipment\
**Created:** [May 14, 2025, 2:49pm UTC](https://forum.backyardbrains.com/t/how-does-the-roboroach-backpack-work/82 "2025-05-14T14:49:20Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![marija](https://forum.backyardbrains.com/user_avatar/forum.backyardbrains.com/marija/32/57_2.png) [@marija](https://forum.backyardbrains.com/u/marija)\
**Post date:** [May 14, 2025, 2:49pm UTC](https://forum.backyardbrains.com/t/how-does-the-roboroach-backpack-work/82/1 "2025-05-14T14:49:20Z")

</div>

The _ **RoboRoach** _ operates using **PWM (Pulse Width Modulation)** with controlled amplitude via a **digital potentiometer**. Instead of directly regulating stimulation **current** , the system delivers a **biphasic PWM signal** to the cockroach’s antennae. This allows voltage to be alternately injected and removed, which avoids DC biasing and prevents harm to the cockroach.

### Variable Stimulation Voltage

The stimulation voltage is not fixed; rather, it varies based on the **frequency of the stimulation pulses** and the **overall signal amplitude** , both of which are influenced by several **variable factors**.

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### Current Pathway

The electrical current follows this path:

1. A **3V DC battery** supplies power.
2. Power reaches the **microcontroller** , which outputs stimulation pulses via a **GPIO pin** (at battery voltage), controlled through a smartphone app.
3. The signal passes through a **digitally controlled variable resistor** (digital potentiometer), which sets the **pulse amplitude**.
4. It continues through a **series capacitor** , which:
  - Shapes the current waveform
  - Prevents **DC biasing**
  - Improves **biological safety** by reducing electrolysis and tissue damage

5. The current flows through a **platinum wire electrode** , connected to the cockroach’s antenna. Impedance here varies with insertion depth, contact quality, and tissue interface.
6. The signal travels through the **cockroach’s body** , which has **biological and variable impedance** based on the individual specimen.
7. The return path completes through the **ground** back to the battery, which includes some **equivalent series resistance (ESR)**.

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### Impedance Variability

Because of **variable and uncontrolled impedance** , particularly from biological tissue and electrode contact, the **exact current** the exact current through the antenna cannot be accurately known or controlled.

- The _ **RoboRoach** _ system modulates **frequency and amplitude** , but not the current directly.
- This design accounts for biological variability while maintaining safety.

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### More Information

For detailed circuit schematics and technical documentation about the _ **RoboRoach backpack** _, please refer to the official PDF:

🪳 **[RoboRoach v1.1b Technical Document (PDF)](https://files.backyardbrains.com/retired/files/RoboRoach.v.1.1b.pdf)**