Archive for the ‘Ham’ Category.

Pressure, temperature and humidity sensor based on MS5637 HDC1080

This is anothe small module to measure air pressure, temperature and humidity. Two sensors are on-board: MS5637 and HDC1080. Microcontroller is small cortex M0 in TSSOP-20 housing from STM: STM32F070CxP. The SN65HVD72DGKR provides RS485 interface functionality with half duplex mode. Voltage regulator, reverse polarity protection and some LED indicators are provided on-board. Complete module is 10x55mm, produced on single-sided PCB, easily producible in every home lab with proto-PCB capability.

RH, T and air pressure sensor with RS485

RH, T and air pressure sensor with RS485

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USB to RS485

Testing of sensors with RS485 using PC without proper interface is not possible. Since RS232 interfaces are very rare, the interface should be hooked to USB. The interface between USB and RS485 can be soldered with one of the many FTDI interfaces with added RS485 driver, or bought as assembled module. There is always the third option. I made it from scratch.

I took smallest STM32F0 with USB and UART interface. The best thing with UART in the STM32F0 is that signal for driver enable is provided within hardware. The complete pinout of the microcontroller is:

pinout

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SiLabs Si7013 humidity and temperature sensor

I got samples of Si7013.

The Si7013 I2C Humidity and 2-Zone Temperature Sensor is a monolithic CMOS IC integrating humidity and temperature sensor elements, an analog-to-digital
converter, signal processing, calibration data, and an I2C Interface. The patented use of industry-standard, low-K polymeric dielectrics for sensing humidity enables the construction of low-power, monolithic CMOS Sensor ICs with low drift and hysteresis, and excellent long term stability. The humidity and temperature sensors are factory-calibrated and the calibration data is stored in the on-chip non-volatile memory. This ensures that the sensors are fully interchangeable, with no recalibration or software changes required. An auxiliary sensor input with power management can be tied directly to an external thermistor network or other voltage-output sensor. On-board logic performs calibration/linearization of the external input using user-programmable coefficients. The least-significant bit of the Si7013’s I2C address is programmable, allowing two devices to share the same bus. The Si7013 is available in a 3×3 mm DFN package and is reflow solderable. The
optional factory-installed cover offers a low profile, convenient means of protecting the sensor during assembly (e.g., reflow soldering) and throughout the life of the product, excluding liquids (hydrophobic/oleophobic) and particulates. The Si7013 offers an accurate, low-power, factory-calibrated digital solution ideal for measuring humidity, dew-point, and temperature, in applications ranging from HVAC/R and asset tracking to industrial and consumer platforms.

I prepared prototyping board with STM32F0 and line RS485 driver:

rht  pcbrht0

 

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Affordable pluviometer part 2 – strain gauge measurements

Affordable precision pluviometer PART 1 (introduction and construction) is here.

Here are first analog measurements of the affordable precision pluviometer:

mL uV uV/mL
0 550
10 568
30 606 1.87
50 643 1.86
100 736 1.86
200 924 1.87
300 1109 1.86
400 1296 1.87
500 1483 1.87
600 1672 1.87
650 1762 1.86
700 1853 1.86
750 1949 1.87

The measurement setup was: measuring graduated cylinder (4) strain gauge sensor (3) from kitchen scale, power suuply (2) and digital multimeter (1):

meas1

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Anemometer without moving parts

Somewhere in year 1995 I had idea for anemometer without movable parts. I forgot about that and recently I started building weather station for the vine yard.  Now it’s time to transfer that idea to reality.This is the sketch from that time:

an2

I am working in company HYB in R&D department. My experience with pressure sensors is longer than the anemometer idea (more than 20 years). Our main products are sensors. We have industrial pressure sensors for extremely low pressures. Lowest full scale pressure sensor goes as low as 1mbar (one millibar!). Just for impression: this is equal to 1cm of water column – one cm under the water surface is 1mbar pressure. The model, most suitable for annemometer based on wind pressure measurement is HPSD 3000:

The sensor has 15 bits I2C output  for pressure and temperature via I2C interface. The sensor is available through our distributor or ask directly here.

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Low cost sun shield for weather sensors

The white plastic radiation shields that protect the temperature, humidity and other sensitive sensors from any direct sunlight can be built for bargain. I started with trays from local garden shop. They sell for about 10 cents per tray with diameter 120mm (5 inches). About 10 trays were CNC machined:

shed1

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12V Power supply

12V high current linear power supply is very useful for HAM applications. I designed one based on s53mv schematic. The circuit is somehow odd because regulation transistors are in negative side of the current loop. Main reason for that is the collector or source of the transistors, which is connected to the housing of the transistor. To avoid isolation of the transistors from the heat sink it is better to have the housing, heatsink  and the transistors connected to negative rail of the power supply. It is similar to the car, where negative pole is connected to the chassis.

pcb pcb1

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Affordable pluviometer (rain gauge)

Today I started with realisation of some affordable weather sensors. First one is pluviometer or rain gauge. My idea is to attach some self draining container on the strain gauge. I salvaged one sensor from old kitchen scale (scrap from some other very interesting project).

First I drew my idea on paper:

IMGP0350

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3D printed Loop antenna

Branko, one of the famous experts for old(ish) radio devices designed magnetic loop antenna, which can be 3D printed. Here are complete instructions in german language:

Germany-Flag-iconLoop Antenne aus dem 3D-Drucker

Slovenia-icon Slovenski opis (in Slovenian language)

Mini CW Keyer / QRSS beacon V1.1

I designed dedicated PCB for the CW keyer. The project is very similar to the version made on prototyping board.

keyer pcb

Here are the updates:

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