BUTag-Mjolnir

I. Description

Backgrond

Perhaps most people still have limited knowledge of UWB. However, you must have heard of AirTag, which precisely uses UWB and combines with BLE FindMy to achieve the function of location tracking.Recently we have launched a brand new UWB module - BU03. With curiosity, we made this BUTag - Mjolnir.

Project Brief

BUTag is a UWB locator. With its precise ranging function, it can be accurately found using an iPhone. Its ultra-low standby power consumption means you don’t need to charge it for an entire year.

Its small size allows it to become a pendant on your keychain. It also looks good when hung on a bag.

You can see the distance to BUTag in real time on the mobile phone app. Some mobile phones can even see the direction of BUTag.

If your bag or key cannot be found at home, it can be located through BUTag. If it is lost outdoors, satellite positioning can also be combined to find its specific location.

Note: Currently, it cannot achieve trajectory tracking yet because we haven’t developed the FindMy feature.

II. Hardware Design

The hardware of the entire project consists of two parts: the main board and the battery power supply board.

Mainboard

• UWB module：BU03——Click-to-buy
• MCU：nRF52832——Click-to-buy
• Battery：360mAh, Polymer lithium battery
• Antenna：Customized 2.4G PCB antenna

Battery Charging Board

• Charging interface: Type-C_16p. (It is recommended to use 4P.)
• Charging chip: TP4057, SOT23-6 package.
• Charge current：400mA
• Indicator light：Side sticker RGB(common anode)
• Charging：Blue
• fully charged：Green

Install Fittings

• Thumb nut（M2*2*3）
• M2 screw（M2*3*4）
• Magnet（6*2*1mm）

Hardware Connection Indication

Installation Position Of Knurled Nut

Magnet Installation Diagram

III. Part Description

1. Hammer shell and antenna

2. battery

3. battery panel

4. BUTag mainboard

5. locating rack

6. lid

IV. Assembly Process

V. Instructions

Test App——Qorvo NI Background

Directly in the App, select the device with the Bluetooth name “NRF52832DK(xxx)” and perform pairing connection to see the distance to the BUTag-Mjolnir.

Charging

The battery capacity of the BUTag-Mjolnir is 360mAh. There is a hidden Type-C charging port on its side. After opening the cover, the BUTag-Mjolnir can be charged.

Performance Parameters

• Ai-Thinker BU03 UWB module
• MCU：NRF52832 BLE chip
• Connect UWB distance：5 meters (stable), maximum 13 meters.
• Standby power consumption: about 30 microamps.

The standby current is 30uA. Let’s calculate how long a 360mAh battery can last?

VI. Design Drawing

BUTag_V1.1

Schematic Diagram

PCB