Fresh hacks every day
[Nick] and [Simon] both have home security systems with a monitoring service who will call whenever an alarm is tripped. For [Simon] this ends up happening a lot and he wanted to change the circumstances that would trigger a call. Because of company policy the service is inflexible, so he and [Nick] went to work cutting them out of the loop. What they came up with is this custom electronics board … [Read more...]
Nope, no microcontroller here, just a full-blown cellphone used as the brains of this little robot. The secret behind how it works is in the sounds the phone makes. The touch tones, known as DTMF, are monitored by the circuit mounted on the front half of the chassis and are responsible for driving the motors. [Achu Wilson] built the circuit around an MT8870 chip which decodes the DTMF sounds … [Read more...]
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. If it goes low and does not go … [Read more...]
[Colin] wanted a way to reliably control an Arduino via ham radio. One of the easiest methods of automated radio control makes use of Dual-Tone Multi-Frequency signalling. To those who aren't into amatuer radio you probably recognized DTMF as the touch-tone system for telephone communications. [Colin] built a shield that has an audio input and can decode DTMF signals. The hardware is based … [Read more...]
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