Speedometer with ATtiny85 and OLED display

2 months ago 329
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Description

Compact speedometer with OLED display and temperature measurement. It features an ATtiny85 uC with USB programming and battery charging and protection circuitry. I will be using it to measure the speed of my bicycle and determine the temperature around me on my rides. The project consists of 2 pcbs: the sensor that will be mounted on the wheel of my bike and the actual speedometer. The wheel sensor sends radio pulses via the H34A transmitter module each time a magnet passes through the Reed sensor. Each pulse will be then received by the H3V4F 433MHz receiver integrated in the speedometer board. The ATtiny85 uC calculates the speed of the wheel and constantly reads the temperature using the TC74A sensor which then prints the values on the oled screen. It can be programmed using the USB interface. The uC can also read the battery voltage. The speedometer circuitry will be supplied with a LiPo battery. The charging and protection circuits are based on a LiPo USB charger board commonly found on Aliexpress. I also thought of replacing the TC74A sensor with a more professional BME280 IC from BOSCH which measures temperature, humidity and altitude, but I did haven't played with it much. This alternative still remains here though.

Documents

Schematic

Speedometer

Layout

BOM

ID Name Designator Footprint Quantity
1 1N4148WS T4 D1 SOD-323 1
2 4.7K R1 0805 1
3 1uF C4,C5 0603 2
4 REED sensor U5 REED-RELAY-L14-2P 1
5 XC6206P332MR XC6206P332MR,XC6206P1MR SOT-23(SOT-23-3) 2
6 3.6V D2,D3 SOD-323_L1.8-W1.3-LS2.5-RD 2
7 4.7uF C2 0805 1
8 H3V4F-433M U4 H3V4F-433M 1
9 390K R11 0805 1
10 2.2uF C3 0805 1
11 TC74A0-5.0VCTTR U6 SOT-23-5 1
12 - SW2,SW1 KEY-TOUCH-SMD-6.0*3.5*H 2
13 47uF C8 CASE-C_6032 1
14 1k R4,R16,R17 0805 3
15 10k R9,R21,R22 0805 3
16 ??? R10 0805 1
17 2k R13 0805 1
18 100 R14 0805 1
19 68 R18,R19 0805 2
20 1.5k R20 0805 1
21 15k R12 0805 1
22 56k R15 0805 1
23 H34A U7 H34A 1
24 Header-Male-2.54_1x1 P3,P1 HDR-1X1/2.54 2
25 ATTINY85V-10SU U2 SOIC-8_208MIL 1
26 PMEG3050EP,115 D4 SOD-128_L3.7-W2.5-LS4.7-RD 1
27 17- LED1 LED-0805 1
28 1uF C6 0805 1
29 1u C7 0805 1
30 0 R2,R3 0805 2
31 DW01A-G U3 SOT-23-6 1
32 10uF C1 0805 1
33 U-MICRM05P-BF10 USB1 MICRO-USB-SMD_5PIN-H-FEMALE-PITCH0.65-L_U-MICRM05P-BF10 1
34 FS8205A Q2 TSSOP-8_3X4.4X065P 1
35 OLED U9 OLED 1
36 BME280 U8 LGA-8 1
37 TP4056 U1 SOP-8_L4.9-W3.9-P1.27-LS6.0-BL-EP 1
38 10nF C21,C9,C10,C11 0805 4
39 100nF C24 0805 1

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