The easiest headlamp You will need:
SD card case
small piece of adhesive tape
+ half an hour of work :)
Behringer Graphic Equalizer EQ700 - modified to my own
(always EQ present, increase gain after rock the pedal)
bass drum - better woof sound, no feedback issues
digital effect processor for electric banjo
Input circuit for Winscope
are few good
freewares usable as audio signal oscilloscope. One of them is
Oscilloscope 2.51 which uses PC soundcard input as signal
Disadvantage of commercial souncards is AC coupled input, but there is
not so important for measuring AC signals (music and sine without DC
offset). Important thing at repairement of an audio equipment is right
measuring the AC voltages (Vp-p) to set right gain etc. I designed easy
input circuit with voltage reference, all supplied from USB.
One switch ON/OFF control
is lot of schematics about
control relays, lights, etc. by one momentary switch (or pushbutton),
but these are the simplest with 555 timer IC and 4069
(or 7404) hex inverter.
Another one is direct powered from 230V AC, always OFF after power
restart. Resistors 120k and 4k7 have not exact values, they must be set
according to ON-OFF characteristics of used relay.
the LEDs have not linear current-voltage characteristics and
their voltage is depended on temperature, they must
powered by constant current source. Ordinary constant voltage source
(like battery) can damage the LED. I know, the serial resistor can be
simple solution, but only for higher ratio Source
voltage to LED voltage (but this is not effective because of too much power loss
across the resistor).
I designed (and also tested) simple current source for one, two, three
or more LEDs. Just put this circuit between +12V and anode
~22mA current will be flowing through the LEDs and it won't be
too depended on source voltage, temperature or number of LEDs.
12V LED bulb for car
I changed (third time in one year) the bulbs in my rear lights (because
of compulsory day-lighting in our country), I build very simple LED
bulbs which have intensity of light comparable to original 10W tungsten
bulbs. I know efficiency is under 50% because of balancing
resistors, but total current consumption is about 50mA at 12V. Much
lower than 840mA with original bulb. I used two SMD LEDs SPMWHT5606
(5200 mcd, 120°, 3x20mA) built in old bulb base.
CONTROLLER for motors, bulbs, etc.
I have bought cheap RC boat without speed control.
I found that it has 4-channel RC system, but only 3 channels
were used (for left motor, right motor and both motors).
The unused 4th channel inspired me to build power controller. Now I can
select by remote one of 4 levels of power.
There is 555-based PWM controlled by voltage level set by counter/current summator/PNP transistor.
Input must be connected to output of decoder (logic levels can be 3.3-5V for High, and 0V for Low)
You must disconnect original ground wire from motors and connect it to
OUT. Power MOSFET will be switching to ground with selected duty cycle.
Here you can see the video how it is working.
Infrared to RF converter
If you need to increase the range of your IR controlled device, you can use 434 or 868 MHz hybrid RF modules.
I designed and tested following circuit and it works fine.