Hack Correlation

This is just a reiteration of my post on  http://www.eevblog.com/forum/ . Since then some people have picked up the challenged and designed new firmware for the microcontroller. Let me explain. The module is a cheap (2-3$) 0-30V voltmeter. It has a 3-digit output, is pretty accurate and begs curiosity with it's TXD/RXD soldermask labels. The inside sports an STM800S3F3 chip with nice features: 2.95-5.5V supply voltage 16 Mhz internal oscillator 3 timers 4 CCP/PWM modules 5-channel 10-bit ADC UART, SPI, I2C 8k Flash, 1k RAM Thoughtfully, the programming/debug port is also broken out, just not labeled. The pinout would then be:   SWIM / PD1 (HS)   TX / AIN5(HS) / PD5   RX / AIN6 (HS) / PD6   NRST   VDD   VSS The board also includes a 3V/30mA linear regulator that can take up to 30V. All-in-all a very cheap development board that can be used for a lot of stuff Here's a close-up picture of the board under strong light ...

Update: if you came here looking for a fix to the annoying beep I might have one - if you are feeling handy: take the unit apart, desolder one wire from the battery terminal, discharge the capacitor (by touching the disconnected wire to the other wire) and solder it back on. Take care not to short the battery, you only want to discharge the circuit with the battery disconnected. If you do not understand perfectly what you need to do then please do not attempt this! This has 'fixed' one of my units (since 6 months) and has quitened another one for ~2 months. Back to the original post: On of the my smoke detectors - installed by the landlord under legal obligation - started acting up by emitting annoying short beeps and random intervals, moreso during the night. The producer boasts a 10-year service lifetime, smoke detection as well as heat detection. Since they are the "non-user-serviceable" type nothing else remains than to take it apart and see wha...

I'm working on a small project in which I'm trying to find out if I can output a sound on a piezo while reading the force exerted on it. It's like a small piano where the input is also the output. I did something similar with LEDs where I measured the light level by first reverse polarising the led and then measuring the discharge time (capacitance). To have an idea with what levels I'm dealing some measurements were in order. Two sets of measurements were taken, one with the original molded plastic housing and one with the housing removed and two wires solder to the piezo. I'm using a normal buzzer, the cheapest I could find, so that I can buy several of them. Raw buzzers should be 10x cheaper than what I paid. This is a light tap on the table while the sensor is sitting about 1m away pressed against the table. The housing was on. Around 1Nm of force from a lighter. A stronger tap under the same conditions, around 5Nm. The same stronger tap...

This project is taking longer than anticipated even though it was supposed to be something simple. I will publish a schematic of the complete circuit in the near future (this year) but in the meantime there is still the slow process of troubleshooting. Safety considerations: the complete circuit is not isolated from mains so testing is pretty critical. I have been feeding 3.6V to test the low-voltage part but in the end it will have to be hooked up to 220V the boiler / water heater can only take a limited amount of pressure. If the thermistor is not properly calibrated in software there is the risk of a scalding hot water explosion With that being said there is some small but steady progress being done. The MSP430 has a some strange power requirements that are not properly documented. The VCC supply  needs to rise with >1V/ms otherwise it gets into an undefined state. That undefined state might also mean that some GPIOs are high, causing catastrophical failure. C...

My TV has a quite complex set of features, none of which work particularly well. Except perhaps using it as a PC display. Input latency is quite bad, ranging from over 200ms in normal mode to 100ms in "gaming" mode. The latency can easily be tested by going to this link and making a picture of both displays (native and external) at the same time, preferably with a flash, in order to shorten exposure time. There's a half-assed [HBBTV] implementation that crashes once in a while, a horrible YouTube app that takes 1-2 seconds to react to keypresses, a barely-workable DLNA implementation and barely-acceptable USB media integration. Oh, it also does triple-tuner TV, but I don't watch TV. Sometimes I'm just wishing they would have stuck with a Linux, WinCE or Android implementation with freeware apps instead of reinventing the square wheel each time. What's worse, each of these apps (TV, DLNA, HBBTV, YouTube, USB media) seems to be written by a diff...

Zoom G1 I got this unit essentially for free a few years back after getting rid of my VooDu Valve which was too expensive/overkill. It's a nice little unit great for practicing guitar and has the added bonus of foot switches (the two big knobs at the bottom): This unit has seen better days and it kept switching itself off or resetting once in a while whenever the cables were moved. Also, it didn't want to work on battery power.

In the first part I identified the problem leading to the unit overheat: a design decision consisting of dropping more than 10 Watts on a couple of 3W resistors. I've thought of several ways to address the issue: change the 5V rail to a switching design put bigger resistors and mount the 7805 on a heatsink have a switching or linear preregulator that drops 12V to a more manageable 7-9 Volts I have a few switching supplies bought from ebay at around 2-4$ each based on the LM2596 reference design. However they might be noisy and I'm not sure how well they handle high loads. Should be good enough for charging the USB and anyway the 1.8V and 3.3V lines go through linear regulators first, cleaning them of noise. The bigger resistor solution would also work but I did not have any 10W resistors at hand and I'm not sure they would fit in the small space between the CD tray and the case. Since I have a few LM7808 and LM7809 from scrap I decided to go with the third solut...