Fresh hacks every day
This pulse oximeter is so simple and cheap to build it’s almost criminal. The most obvious way to monitor the output of the sensor is to use an oscilloscope. The poor-man’s stand-in for that is a sound card, which is what [Scott Harden] demonstrates in his write-up.
It uses a concept we’ve seen a few times before. The light … Read the rest
We’re all familiar with IVRS systems that let you access information using a touch-tone telephone. [Achu Wilso] built his own version which uses a cellphone, microcontroller, and computer.
The cellphone is monitored by an LM324 op-amp with an attached 555 timer chip. When a call comes in the voltage on the headphone output goes high, activating the timer circuit. … Read the rest
[Christian Doran] wanted some blinky goodness to go along with the tunes on his PSP. He built a VU meter circuit around a couple of LM324 op-amp chips and fit it into the UMD space on the back of the PSP. Using surface mount LEDs and some fine wire he lined up a string of indicator lights round the circle … Read the rest
[Manekinen] built a very responsive spectrum analyzer. The components at the party are what you’d expect, an ATmega8 does the hard work interpreting data from the LM324 op-amp. This build stands out because it is fast and configurable. In fact, the explanation of the calibration process is where this project shines.
Instead of using water, an HD44780 module … Read the rest
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