LongRa Q & A

Will I need an Arduino in addition to the LongRa board?

No, the LongRa board includes an Arduino Zero and can be used straight away with the Arduino program. The Technical Documentation describes which pins may already be assigned to LoRa, buttons, etc.

What is the maximum voltage for the Arduino pins?

The external input voltage must not exceed 3.6 V. The output voltage of the pins depends on the power supply and the battery condition, and can range from 2.1 V to 3.6 V, typically approx. 3 V.

How much power can the 3.3 and 5.0 V connector supply?

The integrated voltage converter (booster) converts the battery voltage to 3.3 or 5.0 V. Either 3.3 V or 5.0 V can be switched on via software. In addition, the VDD voltage, which corresponds to the battery voltage, is available. The board is designed for a maximum output of 150 mA from the 3.3 V or 5.0 V connectors. At a battery voltage of 2.5 V (e.g. rechargeable cells) this corresponds to a battery drain of 300 mA.

Can I completely switch off the power supply from external sensors?

Both the 3.3 or 5.0 V power supply can be switched off completely, so that external consumers, e.g. the particulate sensor, cannot draw any current.

Which display is compatible with the connector?

It is a 3.3 V SPI display connector. Basically, various SPI displays can be used. We have tested the following display which is available at AliExpress.

How much power does the external display require?

This is basically dependent on the display content; the power consumption is 10-25 mA at 3.3 V operating voltage. By a software command, the display can be cut off from the power supply, so that it consumes no power at all. A special hardware wiring is implemented on the LongRa board for this purpose, saving energy and extending battery life in operation.

What is the meaning of the ID and the code on the back of the board?

The ID is a unique node number (device ID), which each device needs to have when communicating via the RadioShuttle protocol. The 8-digit code ensures that the ID is compatible with the board.

Can I specify by myself an arbitrary ID (device ID) per board?

No. The ID and the code printed on the back of the board must be used, otherwise it will not work. Of course, when sending a message, the device ID of the receiving device can be specified freely.

Can I power the LongRa board also with AAA batteries?

Yes! AAA batteries can also be used. Suitable battery holders whose board connectors are compatible with the existing AA battery holder are available from Rapid Electronics. These can simply be replaced. If an external battery holder is used, please ensure that the wiring from the battery to the board is as short as possible.

Can I also use rechargeable NiCd batteries?

All common rechargeable NiCd batteries can be used. Usually these cells can only deliver a voltage of approx. 1.2 V per cell, meaning 2.4 V in total. Operating the LongRa board with rechargeable cells is fully supported. Rechargeable cells can be advantageous for those consumers with a particularly high power consumption because they are able to deliver more peak power. Usually regular non-rechargeable batteries are better suited since they show a considerably lower self-discharge.

Is the operation with a USB power pack possible?

A USB power supply is supported and works perfectly. Switch the jumper to the right. However, when using a power pack two drawbacks have to be taken into account: In the “Node Offline” mode the LoRa board draws so little current that various power packs regularly shut down automatically because they think the consumer is no longer connected.

Another drawback is that the operation by use of a power pack is not energy-efficient, as the power pack internally converts its LiPo battery (lithium-ion polymer) battery voltage from 3.7 V to 5.0 V, the LoRa board then converts the 5.0 V to approx. 3.7 V. These two conversions unnecessarily consume energy.

Can I power 230 V consumers with the LongRa board?

Yes. External solid-state relays (SSR) can be provided with a source voltage of 5 V by the LongRa board, and output 230 V, to power a connected device.

What is the maximum allowed battery input voltage?

The battery connector input voltage can range from 2.1 to 3.6 V. More than 3.6 V is not allowed and will lead to hardware damage.

Are more powerful lithium batteries advantageous?

Basically, simple AA batteries are absolutely sufficient for proper operation. High-performance batteries do not provide a significant advantage. Lithium batteries do have the advantage that they will work better in cold environments (outdoor use with freeze).

Can I measure the battery voltage?

LongRa boards starting with rev. 7.5 support reading out the battery voltage. For older LongRa boards please read this Tech Info.

Can I deactivate the external power supply LED?

To deactivate the LED, the solder bridge beneath the LED can be interrupted (remove solder). Then the LED is deactivated for USB or external power supply.