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TWE-EH SOLAR

Latest version
TWE-EH SOLAR (Energy Harvest Solar) is a power management module that converts light energy into electrical power for use as a power source for TWELITE. It can be used as a replacement for batteries to operate TWELITE.

Power radio transmission with the force of light!

Dedicated to TWELITE series! Energy harvest control board TWE-EH-S

With pin headersTWE-EH-S-DI

With pin headers
TWE-EH-S-DI

Without pin headersTWE-EH-S-DP

Without pin headers
TWE-EH-S-DP

Thank you for purchasing our product.

Features

  • An energy harvest control board designed for use with TWELITE modules.
  • Stores energy from solar panels in capacitors and uses that energy to operate wireless modules for very short periods.
  • Built-in circuit charges excess energy to storage devices (electric double layer capacitors), enabling continuous operation even at night when solar panels are not generating power.
  • Various solar panels can be used with external circuits or additional resistors.

Precautions for use

This evaluation board is designed to be used in combination with TWELITE modules.

Software acquisition

Please write the Wireless Tag App (App_Tag) firmware to TWELITE.

Available solar panels

As a guideline, solar panels with open-circuit voltage of 4V-6V and maximum output power of 300mW or less can be used.

To use solar panels with maximum output power of 10mW or more, connect an additional resistor \(R_{EX}\) between TWE_VCC and EX_REG. This prevents failure or fire due to overvoltage or overcurrent.

The value of the additional resistor \(R_{EX}\) can be calculated using the following formula:

$$R_{EX} [Ω] \leqq \frac{11.5}{Solar panel maximum output power [mW]} \times 1000$$

Let’s get it running!

Simple wireless thermometer

Please configure the circuit as follows:

Example of transmitter circuit

Example of transmitter circuit

By writing the Wireless Tag App (App_Tag) to the TWELITE module and setting the sensor type to 0x11 LM61 analog temperature sensor, data transmission can be performed.

For the parent device, write the Parent/Repeater App (App_Wings) and match the frequency channel and application ID.

How it works

Voltage changes on each pin

Voltage changes on each pin

  1. Energy from the solar panel is charged to the built-in capacitor C1 (220uF).
  2. When the voltage \(V_{C1}\) of C1 reaches approximately 2.9V \(=V_{ON}\), TWE_VCC is connected to GND and TWELITE starts operating.
  3. TWELITE immediately sets the DO1 \(V_{BOOT}\) output to Low right after startup.
  4. TWELITE performs wireless transmission.
  5. After wireless transmission, TWELITE enters sleep state.
  6. When the voltage drops below approximately 2.0V \(=V_{OFF}\) due to insufficient energy supply, TWELITE stops operating. The Low output of DO1 \(V_{BOOT}\) is released and returns to step 1.

In steps 4’ and 5’, it repeats the operation of wireless transmission after wake-up from sleep, then going back to sleep.

Pin assignment

Signal namePin numberPin numberSignal name
TWE_GND116TWE_VCC
BOOT215EX_REG
BYP314VC2
(-)413RSTN
(-)512C2+
(-)611(-)
(-)710EX_C1+
(-)89(+)

TWE_GND

Connect to TWELITE’s GND.

BOOT

Connect to TWELITE’s DO1.

For wireless tag app. For act, etc., connect to any pin

Set to Low state promptly after TWELITE startup. Voltage conditions follow TWELITE specifications.

BYP

Connect to TWELITE’s DO2.

For wireless tag app. For act, etc., connect to any pin

When set to High state, it bypasses the diode connected between the storage device and TWE_VCC.

When power is supplied to TWELITE with the storage device at 2.3V, TWE_VCC becomes approximately 2.0V due to diode voltage drop and operation stops. By bypassing, TWELITE can operate until the storage device voltage drops to approximately 2.0V. Voltage conditions follow TWELITE specifications.

GND / (-)

Connect the negative terminals of the solar panel, storage device, and capacitors added to EX_C1.

(+)

Connect the positive terminal of the solar panel.

EX_C1+

Connected to the positive terminal of the built-in capacitor C1 (220uF).

By adding a capacitor between EX_C1+ and GND, it is connected in parallel with the built-in capacitor C1 (220uF), increasing the capacity. The voltage range is 0-3.6V.

C2+

Connect a storage device for charging excess energy between C2+ and GND. The voltage range is 0-3.6V.

For connection details, see Making it work at night too!.

RSTN

Indicates TWELITE’s operating state. (Hi: Operating, Low: Stopped)

VC2

When monitoring the charging status of the storage device, connect to TWELITE’s AI1.

For wireless tag app. For act, etc., connect to any pin

VC2 divides the voltage of C2+ with two resistors (10MΩ). Additionally, to stabilize TWELITE’s voltage measurement, a 0.1uF capacitor is connected between VC2 and TWE_GND. By multiplying TWELITE’s VC2 reading by 2, you can obtain the storage device voltage.

EX_REG

See Available solar panels.

TWE_VCC

Connect to TWELITE’s VCC.

Making it work at night too!

Simple wireless meter (with excess energy charging circuit)

With only C1, the wireless module’s operating time is limited, but by adding a capacitor to EX_C1+, the operating time can be extended.

Example of transmitter circuit

Example of transmitter circuit