All Questions

5 views

Play audio from raspberry pi through my car's disc changer

I'm interested in trying to buy a raspberry pi and create a small bluetooth / airplay type module that I can plug into my car somehow and get wireless audio streaming. I don't necessarily care about ...
23 views

I guarantee this one will be fun - Need help putting several circuits together into one

So I did my best to annotate the schematic with what I'm trying to do. Where I'm really running into trouble is past the output of the 555. This is basically a control circuit for a camera's ...
25 views

Logic low not low enough

I'm having an issue where the "low" level being output from one device isn't low enough for the device on the other end to interpret it as such. I'm guessing I'm not the first person to have this ...
18 views

I have a power over Ethernet design using the SI3402 PoE PD chip to generate 3.3v for a pic 18F67J60. The switched mode voltage converter in the SI3402 is a little unorthodox in that it switches Vss ...
24 views

Best way to take 110V down to use with 12V motor

I'm building a lamp that continuously spins, and wish to use a 110V wall outlet to simultaneously power the lightbulb and a small motor. What is the most efficient way to do this? I'm new to ...
12 views

Simulating a linear voltage regulator with ngspice

I am trying to simulate a simple linear regulator using gschem and ngspice. However, my output voltage varies by over a volt as my input voltage goes from 10V to 20V. Can I reduce this swing in the ...
21 views

What microcontroller board to use for TCP and UDP Ethernet communication? [on hold]

I'm not really experienced, so I need a board that makes stuff easy. The microcontroller is supposed to read data from a power sensor, do some control processings and drive a motor (for the initial ...
7 views

Arduino if else code [migrated]

I have made this If-Then-Else code, but it doesn't work. First I tough only the analog code is wrong, but if I take a digital port, the code doesn't work either. What did I do wrong? ...
14 views

Running a load off a solar panel connected to 2x 12V batteries.

I am having trouble figuring out what relay I should be using for my solar panel set up. I have a solar panel running to a solar charge controller. I then have the controller running into a relay. ...
43 views

Output of a NAND gate

Above is a TTL totem pole output NAND gate. There is a 120 ohm pull up resistor there. Since it is called pull up, can we say that the HI output will be connected to a very high input impedance? If ...
15 views

Does 120V frequency input signal required for CE low voltage Directive?

My device has a 120VAC with 1mA frequency Input. The device run on 24 VDC. Does it need to be complice with Low Voltage derective for CE self certified?
50 views

What is __bit in the XC8 C compiler?

Let's take an example: extern volatile __bit TRISB0 @ (((unsigned) &TRISB)*8) + 0; I believe this is pointing TRISB0 to ...
30 views

Professional Electronics Inventory/Sales Management Software

I'm looking for a piece of software to manage our business. I'm posing the question here because it's an electronics business and so some of our requirements are unique to our industry. We have about ...
47 views

A question on pull up resistors

I'm wondering why pull up resistors in text books are told such that they pull up the voltage to $V_{CC}$. Here is a diagram: When the button is open what will be the input voltage to the micro ...
18 views

Inductance in Transformers inductors

How can I find a transformers inductors value by using the derivative formula? If I want to generate high voltage spikes from a square wave generator of 10V p-p with a source resistance of 50Ω. I want ...
31 views

PCB trace width calculation

Take a look of this product: http://www.hobbyking.com/hobbyking/store/__68694__HK_Pilot_Power_VI_Module_Distribution_Board_And_Dual_UBEC_ALL_In_One_120A_and_10s_.html It says is a 45 by 45 mm PCB, ...
27 views

AND gate made out of NAND's seems to have 25us delay compared to ~20ns

I've made a 3 input AND gate from 4 NANDs in order to daisy-chain 3 motor drivers jrk 21v3 and get the current value out of them. The problem is, the command is sent OK, the driver responds OK with ...
31 views

How to prevent applying power to I/O pins before BBB ready?

From the Beaglebone Black SRM Rev C.1: "DO NOT APPLY VOLTAGE TO ANY I/O PIN WHEN POWER IS NOT SUPPLIED TO THE BOARD. IT WILL DAMAGE THE PROCESSOR AND VOID THE WARRANTY. NO PINS ARE TO BE DRIVEN UNTIL ...
26 views

SMD Component identification by picture

Can anybody identify component on picture? I got it from Farnell instead of FDN306P (i.e. unknown component in bag labeled as FDN306P). . Does exist a site specialized to identification of unknown ...
31 views

Make Bypass with Switches

I have the diagram below, but I don't understand how the switches are hooked up. Is that an special switch, or I can achieve that with an special connection? Thank you!
30 views

LM3915 VU Meter Not working properly

I built a LM3915 (Waiting for LM3916 to arrive) VU Meter based on Sparkfun's tutorial https://learn.sparkfun.com/tutorials/dotbar-display-driver-hookup-guide Problem is, when I plug the power, only ...
207 views

Are all sequential circuits based on cross-coupled NAND or NOR gates?

So far, all the sequential circuits I see in the textbook use cross-coupled NAND or NOR gates. Is it possible to design a sequential circuit without them?
44 views

Triangular wave generation using consant current

I am trying to design a circuit, that will generate a triangular wave from charging/discharging a capacitor with a constant current, but am stuck. I have a power supply of +-12V and +5V, the circuit ...
31 views

I designed a circuit to charge several ipads at the same time however apparently i have a voltage drop across my usb conector that falls to 4.53v instead of 5v when charging 4 ipads, the total current ...
17 views

Toshiba 27a51 tv component video input not compatible [on hold]

I am trying to connect a Dish Network receiver with component output to the Toshiba 27a51 tv's component video input. The the image is scrambled. Connecting the Dish to another newer model RCA tv ...
28 views

BER for BPSK over AWGN Channel [on hold]

A BPSK scheme operating over an AWGN channel with noise power spectral density of $N/2$, uses equiprobable signals $S_1(t) = \sqrt{\frac{2E}{T} sin\ t}$ and $S_2(t) = -\sqrt{\frac{2E}{T}sin\ t}$ ...
44 views

How to run a 6v 4amp motor at slower speeds for long periods of time (2 hrs)?

I am trying to get a project done for Halloween. I am running a 6V 4A motor (from a powerwheels) but need it to run slower. I tried using an adjustable charger and ran it at 3V to slow down the ...
82 views

How do I solder to these pads?

Quick question. I'm trying solder some wires onto the 5 pads (top right of board) in the image. What's the best way to achieve this? I cant get the solder to stick to the board and I have no flux. I ...
30 views

Android Compatible microcontroller [on hold]

I am looking for a micro controller like arduino or Raspberry PI which runs the Android SDK and can access Wifi , 3G and GPS. i am aware that it requires wifi shield and 3G + GPS shield but what i ...
38 views

Input/output characteristics for this diode circuit

Given this circuit: Assume VB = 2V, constant-voltage drop model, and VDo = 0.7V. How to plot input/output characteristics? Here is my try: When the diode is on, we replace the diode with a ...
36 views

Are these amplifiers LT1991 and LT1995 good for prototyping?

Do the above amplifiers fullfill these requirements? ISO 13485, EU-Directive 93/42/EEG Medical Devices, ISO 14971 Risk Management, IIEC60601-1 electrical and EMC tests I want to get the best ...
10 views

LTspice: Noise simulation AND AC analysis in one plot

Is it possible to run a noise simulation and an AC simulation independently from one another and display the results in the same plot? Or better, is there a way to determine the SNR in one single ...
24 views

Comparison of Series and Parallel LC Filters for Noise Reduction

Since there are two basic types of LC circuits that can be used for passing/blocking signals, I'd like to know the differences when using series or parallel LC circuits for noise at a known frequency. ...
28 views

How to improve current control loop in power supply?

I'm working on MCU programmable bench power supply. Its range is 0-50V and 0-3A programmed in 10mV and 10mA increments. It will be published as open hardware and source code that anyone can use it ...
37 views

Shielding not connected to USB connector causes tablet restarts

I have a custom USB cable, USB type A male on one end and a DB-9 connector on the other end (only using 4 pins). The shielding of the cable is connected to the USB connector but not the DB-9 ...
27 views

Bipolar stepper motor (Alfa Romeo 156 speedo) w/ L293D

I would like to use my Alfa Romeo speedo in my simrig, I have got the cluster pinout and the speed signal is coming from the ABS (Just like any other car, my BMW cluster works like charm). The only ...
67 views

Soldering BGA components DIY

If I understood correctly, current BGA components contain solder balls under the package. Do I still need additional solder paste to put on the board, or the amount of solder on the component contacts ...
33 views

Designing 1-to-2 demultiplexing circuit with a custom truth table

I'm trying to build a circuit with following truth table with CMOS logic. Pins are: I and A are inputs ...
60 views

Digital trimmer capacitor

We would like to design an FM transmitter module for Arduino boards. Therefore, we are in need of a trimmer capacitor that can be controlled digitally. Do digital trimmer capacitors exist or do you ...
32 views

Resistance of electric circuit [on hold]

How to get a total resistance of 18 ohm From 2ohm and 4 ohm and 10 ohm and 12 ohm How can I connect them to get 18 ohm
9 views

Sending multiple channels with bluetooth

I have ordered my HC-05 BT modules. My question is this: Is it possible to send multiple channels over bluetooth. For example, stereo sound has two channels. I think i have seen people do this but i'm ...
23 views

How can I render my 2.4GHz antenna directional?

With barely no knowledge in this field, I would like to render my antenna used with Bluetooth BLE devices more directional. I tried to shield the antenna with different kind of metals with no luck. ...
29 views

How does this motor drive circuit work?

The Drive terminals are connected to a PWM signal generated by an arduino micro controller. The purpose of this circuit is to isolate the arduino from the motors to avoid too much current being drawn. ...
200 views

How can I bind a local variable to AVR's rXX register?

I need to have programmable pause with precision as high as possible. To accomplish this I have the following GCC code: ...
41 views

PIC32 does not get UART RX interrupts in xc32 Compiler

I'm trying to setup a UART channel on my PIC32 MCU (PIC32MX470F512). But the code does not reach the ISR at all. I have verified that the PPS (peripheral pin select) is configured properly and the ...
39 views

When is impedance matching necessary? Isn't it much less efficient on all other aspects?

I understand that discontinuities of the physical properties of conductors create reflections much like dioptres reflect a bit of light, but : in which cases does impedance matching become ...
15 views

How is 802.11 (Wifi) received signal strength (RSS) measured and reported to software?

I have looked around for a while now to find an answer to this question, but answers I find do not fully answer my question. I found this response interesting from another question on this site. ...
83 views

Does current flow stop when a capacitor is fully charged?

If I take a 1V battery and a 1 farad capacitor and a bulb and connect them in a circuit. Then will after the capacitor gets charged (not fully charged as that is impossible) will the bulb gradually ...