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Drive relay with opamp!
If you look at the specifications of the LM324 Op Amp, you'll find that it's not guaranteed to be able to supply more than 20mA of current when connected the way you have it. If...
Monday, 30 August 2010 - 19:39
Eagle Gerbers and Excellon Drill Plots?
When creating the gerber files from my Eagle designs, I've found that Eagle does the hole placements in the drill file to four decimal place accuracy instead of the three decimal...
Thursday, 26 August 2010 - 16:19
Driving LED with low voltage
I built a high power LED driver circuit for use in a flashlight I built. The input voltage is 4.5V, and it's driving 700mA into a series string of four 3.4V LEDS in one package....
Thursday, 26 August 2010 - 16:10
switch interface to AVR
If you really do want to put the LED and the switch in the same circuit like that, put the LED in series with the pullup resistor, and use a normally open switch to ground. The...
Wednesday, 21 July 2010 - 12:54
Single input h bridge circuit for motor control.
The first question I'd have is what the voltage and current requirements of the motor are. If they are low enough, there are single chip solutions like the L293. If they are...
Thursday, 15 July 2010 - 14:58
SPI Shift Register
Microchip MCP23S17 and MCP23S08 sound like they might be what you're looking for. The'S17 is a 16 bit I/O port, and the 'S08 is an 8 bit port. Both are bidirectional and use only...
Wednesday, 14 July 2010 - 15:59
Potentiometer causing voltage variation throughout circuit
Looking at the circuit you've posted, I see you have the AREF pin (pin 32) connected directly to VDD. this is supposed to be a 2.56v reference voltage brought out to a pin for...
Monday, 12 July 2010 - 20:09
Encoder Decoder and interrupt
One question about your Tx modules. Do they have the carrier on at all times, or only when sending data? Receivers will lock on to the strongest signal. If the transmitter is on...
Monday, 12 July 2010 - 18:55
How to design something that can last long (years)?
Another factor to consider is battery capacity. A battery can lose as much as half its capacity when it gets very cold. It will regain that 'lost' capacity once it warms up again...
Monday, 21 June 2010 - 19:24
Charge pumps, PWM, and FETs
One method that I haven't seen mentioned would be to use an LM317 voltage regulator and a resistor wired up as a constant current source. Connect the sensor from the output of the...
Monday, 21 June 2010 - 19:16
Interfacing Dot Matrix Display with a Microcontroller
One thing that jumped out on me when I looked at your schematic is that you're not showing the power supply. Are the transistor emitters connected to the same power supply voltage...
Thursday, 6 May 2010 - 14:27

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