Posts by Carl
I have a PCB with an onboard microcontroller that I use to turn on and off a bunch of switches/relays. To control which relay should be on I use my computer to communicate via USART to the microcon...
The ATmega16U2 datasheet suggests putting an external lowpass filter from Vcc (the digital supply) to AVcc (the analog supply). However, the datasheet doesn't specify what type of lowpass filter...
I have built an ECG amplifier that uses an instrumentation amplifier and a driven right leg circuit to attenuate 50 Hz common mode voltage stemming from the body. A portion of the circuit is seen b...
I am an electrical engineering student and I just finished designing an ECG-amplifier circuit. Here is the schematic: - It is fairly simple. Initially, there is a 1st order highpass filter. Then...
I am using the AD620 as instrumentation amplifier to amplify the body's ECG signal. An ECG is a differential signal (measured with two electrodes) and I want a differential gain of Gd=1000 . The ...
Homework problem A MOSFET has a power dissipation of $P_{d} = 10\text{W}$. The MOSFET is mounted on a heatsink. There is an isolation pad between the MOSFET case and the heatsink. We are given t...
According to Signal processing and linear systems by Lathi, the transfer function $H(j\omega)$ does not exist for systems with poles in the RHP: - This makes sense to me, since $H(j\omega) = \fr...
I have the following problem: - Using Wikipedia I find that during CCM we have the relation: - $$\frac{V_{out}}{V_{in}} = -\frac{D}{1-D} $$Solving for $D$ and inserting values gives me $$D...
When I program STM32 microcontrollers I use ST's toolchain which provides all the tools necessary in order to build (and flash) the application binary. The toolchain also comes with ST's own librar...
I am soon finished writing the firmware for a relay control board that will help us automate some of the electrical tests we run at the company I work. In essence, the board more or less just turns...
When recording an ECG signal, the raw signal is taken from the body and sent into an ECG amplifier to amplify the signal to a suitable range and remove common mode and other types of noise. Measur...
What does it mean for signals to have impedance? To me, impedance is kinda like an "extended resistance" that also includes phase shift $$Z = R + jX $$It makes sense to me that components like cap...
How do I handle errors in my embedded system? I have learned that it is a de facto standard for driver functions to return an error code that reveals if the function fulfilled its main purpose or i...
In the R&D section of the company I work for we use a Segger JLINK to communicate and program our devices. We use our own small "converter board" PCB to convert the JLINK 2x10 pin header connec...
I recently read the accepted answer here, by Olin Lathrop: Decoupling caps, PCB layout It talks about preventing an IC from acting as a center fed patch antenna by keeping the high frequency curre...
I built a small breakout board of for an ATmega328p microcontroller. It included an AMS1117 5 V regulator and a CP2102 USB-UART bridge for programming and serial communication. On the board I use a...
A microcontroller can be modelled simplistically as a broad band current source/sink. For example, when the microcontroller wakes up from sleep mode and goes into an application mode where many of ...
I'm designing a PCB to filter and amplify a differential body signal with amplitude 5 mV up to 5 V. The first part of the circuit consists of a first order highpass filter to remove any DC componen...
This problem investigates the behavior of the voltage across the capacitor in response to a step input: - I am asked to find the voltage Vc(t) without the use of differential equations or simula...
I think this site needs to get an aesthetic make-over in order to make users coming back. This may be because I'm accustomed to StackExchange's appearance but to be honest, this site is ugly and u...
