Archive for the 'Hardware' Category

Interrupt driven SHT1x humidity sensor

The Sensirion humidity and temperature sensor has a two wire serial interface to read out the temperature and humidity. It also has a status register which can be set up, e.g. to choose the number of bits of the measured values . This post is about reading the sensors using the  power on defaults. Continue reading ‘Interrupt driven SHT1x humidity sensor’

Arduino library for the AM2302 humidity and temperature sensor

The AM2303 sensor  from Aosong integrates a humidity and temperature sensor. A micro controller can fetch the sample values from the device via a single serial signal line. The measurement resolutions (not accuracy) are 0.1% RH and 0.1 °C.  AM2301, DHT21, DHT22,  SHT15, SHT11 and SHT10 are probably equivalent products. I have tested the library using an Arduino Pro Micro module. You can download the library here . Continue reading ‘Arduino library for the AM2302 humidity and temperature sensor’

Raspberry PI boot time vs memory card

I tested my Raspberry PI  with these 4GB SDHC memory cards. Boot time is what dmesg gives for   smsc95xx 1-1.1:1.0: eth0: link up The cards hold an Arch Linux image, almost identical to the original I downloaded from the raspberry PI site . Continue reading ‘Raspberry PI boot time vs memory card’

NV-RAM for the TS7500 ARM single board computer

Technologic Systems’ ARM single board computers for embedded systems, the 7500 series, may be ordered with a battery backed up real time clock. However, unlike RTC chips used for PC’s these come with no static RAM. I missed this RAM for an application I was working on and therefore modified the board. This made this computer board a perfect fit for my client.

Continue reading ‘NV-RAM for the TS7500 ARM single board computer’

Stellaris Cortex and OpenOCD

I have always had problems with OpenOCD, mainly due to bad documentation out of sync with the code. I got a new evaluation board for the LM3S2965 processor (EK-LM3S2965) last week and gave OpenOCD a new try, and lo, this has become quite simple. Continue reading ‘Stellaris Cortex and OpenOCD’

A small DIY hydro-electric power generator

I was involved with the development of a 5 kW hydro-electric power generator in 1985. It has now run for 25 years and I  publish this description of the plant to celebrate. Continue reading ‘A small DIY hydro-electric power generator’

Pneumatic organ control

I have produced the control system for several pipe organs using electro-magnetic solenoids for the stop actions.  I just finished a new one where we use pneumatic cylinders to provide force. A pneumatic system can actually work without producing much noise if set up correctly. So we are very happy with this new organ in St. Johannes church, Stavanger, Norway. Continue reading ‘Pneumatic organ control’

Store docs in the microcontroller’s flash

When starting out as an engineer, building electronic circuits of many kinds, my mentor advised me to always leave a copy of the schematics within the box. This is a wise proposition, the schematics in the box will probably be up to date and readily available. On the other hand, external documentation may be displaced and even lost during a period of time. This is equivalent to program documentation: Comments within the source file are easier to keep up to date than some external documentation, like flow sheets.

Now I use a board with a micro controller which  flash memory is much larger than what I need for the application. So why not use that spare flash to embed  some docs? Continue reading ‘Store docs in the microcontroller’s flash’

ARM with CAN interface

An open hardware project involving a PCB with an AT91SAM7X128 processor with galvanically isolated CAN bus and power running off 24V DC. All documentation needed for production (schematics, board layout, gerber files) is included in this tar-archive. You are free to use and produce this hardware, see the included license file. This project is also registered with Harkopen.

A fan for my graphic card

My graphic card felt hot to the touch, it needed some cooling. This is not an advanced card, so there is no on card fan. Continue reading ‘A fan for my graphic card’

The ring binder PC

This PC is built into a very simple case: a ring binder. The PC is anembedded controller – not used by humans but independently doing its specialunsupervised job. In this case it wakes up once a day, takes a picturewith a USB camera, stores it and then powers off again. Continue reading ‘The ring binder PC’