# All Questions

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### How to end sending data over I2C by Slave or Master?

Let us say a Slave or Master is sending multiple bytes to the receiver on I2C bus and the number of bytes is not defined before hand. So then how will the sender tell the receiver that it has no more ...
0answers
7 views

### What happens to the waveform when the E3 is enabled in 74LS138 (1 of 8 decoder)?

I tried to understand the function of 74LS138. So here's the schematic So what will happen to the rest of outputs?
0answers
4 views

### Charging battery bank

I have two 8 volt batteries in series to get the 16 volts that I need to run my amp it works fine but I need to know how to charge them I am running a 12-volt system in my truck?
0answers
8 views

### Nodemcu controlling a button on a pcb?

So i am trying to connect this button with a Nodemcu esp8266 (the push button on the bottom side of the pcb in the picture) Can anyone help me to wire this to a esp8266? Also i measure 3.3v whether ...
0answers
16 views

### Is it possible to use J1939 and CANOpen on the same bus?

Please correct me if i'm wrong. The way I understand it, J1939 is based on CAN2.0b and uses 29 bit identifiers. CANOpen is based on CAN2.0a and uses 11 bit identifiers. If for example, you have a ...
1answer
11 views

### Reading Audio from SD Card and playing on DE1_SoC FPGA board

I am trying to read audio a micro SD card which will be stored in the form of a .wav or .mif file. I currently have an audio controller that takes in mic in as input. I want to change that so that the ...
2answers
19 views

### Is it possible to combine Common and GND on a DC/DC converter?

There is an isolated DC / DC converter TMR1222 12VDC will come to the input, The outputs will be + 12VDC and -12VDC When connecting with dual output, there is a "Common" contact Tell me, is this ...
1answer
16 views

### Few Strip of WS2812 with 3V3

I am trying to drive 8 strips of led WS2812 (5V) with a CPU STM32F030. The output from the CPU is at 3V3. So, I used a 2N3906 connected to 5V with resistor. I've got no problem with that. Now,I want ...
0answers
17 views

### I2C High Speed Multiple Slaves Layout

I am working on a system where I need to have 16 I2C devices on one bus. Due to data rates I need to run at 3.4 Mbit high speed mode. Are there any design/layout guidelines to help deal with a large ...
3answers
57 views

### Is there any reason as to why the schematic symbol of comparators is almost equivalent to that of op amps?

They do similar tasks, but they are almost completely different because comparators output digital signals. In that case, I am confused as to why their schematic symbol is almost entirely the same. Is ...
1answer
20 views

### Reduce Phone charger values

I’m trying to modify the output of an old Motorola Phone charger which is rated 5v 500ma and i want to modify it’s output to 1.2v 150ma to charge a small battery . can this be done ? I can’t open the ...
1answer
18 views

### Backup PWM signal for DC fans

Currently, I have a board that powers 4 DC fans. A PWM signal is received from an external microcontroller to control the fan speeds. Unfortunately, the microcontroller sometimes fails to send the PWM ...
0answers
35 views

### Using the same potentiometer for two 555 timers

simulate this circuit – Schematic created using CircuitLab I have two 555 timers hooked up and I want them their duty cycle to be controlled by the same potentiometer. The second one has twice ...
0answers
12 views

### Xhp-2 compatible smt right angle header

Does such a product exist or is there another option? We have a few hundred batteries with jst xhp-2 female connectors and need to connect to pcb we are designing, but we can't use throughhole parts. ...
0answers
21 views

### How do I wire this to a trrs headphone jack [on hold]

I have a pair of Jabra Evolve 80 wired headphones, and the left ear stopped working. I bought a replacement trrs headphone jack, but when I cut off the old jack, there were six wires inside of the ...
0answers
21 views

### Cockcroft-Walton generator [on hold]

I use a reverse-fed transformer for a Cockcroft-Walton circuit. Why doesn't it work? My input is a 2V signal generator, and I want to get 2KV.
0answers
27 views

### Adding LED to anti-audio pop circuit

I have built a slight variation of this circuit listed elsewhere on this site: 5v Electret microphone to PC mute switch pop help I'm using this to add an inline switch to my computer headset - ...
3answers
33 views

### Can I replace a dual section capacitor in a tube amplifier design with two single capacitors?

I was planning on building this schematic, but found it hard to source their 20/20 dual section cap (C3/C4). Could I replace this with two single 20uF caps, or is it a dual-section for a reason?
2answers
33 views

### Single-package DC/DC converters for PoE — good idea?

I'm planning a design where we'll use PoE to power a data acquisition board (essentially, an ADC + microcontroller + ethernet PHY and interface). I look at DC/DC isolated converters to get the 5V or ...
0answers
38 views

### Why is my wiring a fire hazard when we have circuit breakers? [migrated]

A neighbor in my (US) building just found out that his laundry room (and others in the building including mine) are wired incorrectly. When the original washer and dryer were replaced, the dryer ...
2answers
39 views

### How to get an analog signal 0 to 12V DC based on reference 0 to 5V DC?

I have an Arduino witch is creating an analog voltage from 0 to 5V (I used external DAC for it) and I need to use it for the regulation of "big" circuit with 12V DC. So I am trying to get on the "big" ...
0answers
17 views

### Calculating the linear travel per step of an actuator

I am using a linear actuator from Portescape. Part # 20DBM-L, 5V series D1B Bipolar. Datasheet Link, with ST SPIN 220 motor driver datasheet link to drive it, in full step mode. From the datasheet of ...
3answers
70 views

### What benefit are opto-couplers for relay switching providing, if both sides share the same ground?

I wanted to connect some relays to my Raspberry Pi (for 12V, not 230V) and I found the waveshare RPi Relay Board, which has the following schematic: I like that they spend some thoughts on filtering ...
0answers
15 views

### How do determine MOSFET parameters in LTSPICE

I am designing a phase locked loop on LTspice (which I'm new to), but have come across a snag in the procedure: Is there a way to determine the output resistance of a mosfet (as the I'm not able to ...
0answers
22 views

### Exponential circuit in Multisim

I have a circuit which has an exponential function as shown in the figure. I tried to put an anti-log opamp with the diode and BJT transistor, but did not get what I wanted. I think the whole problem ...
1answer
28 views

### Diode ROM with decoder and multiplexers

I have this question on my exam I couldn't answer: A diode ROM has been built using a decoder and multiplexers. If A4A3A2A1A0 = 01001, what is D3D2D1D0? Here is the first schematic: The answer is ...
0answers
18 views

### 555 timed power at high to low edge in battery powered circuit

I have a lovely Atmel touch sensor whose output is high only as long as it's touched. I want both off-on and on-off edges of its output to initiate two 3 sec pulses (and the time between edges is > 3 ...
1answer
44 views

### Recommended air flow and temperature in hot-air gun to recover a MLB from MacBook

First I would like to say I've searched and researched, I think enough, for an old topic that discuss this matter but wasn't able to find any specific information. I've a main logic board from a ...
1answer
40 views

### Control current to one of two loads on PCB

I am currently working on a project where 2 batteries powers multiple components on a board. A raspberry pi, 2 thrusters and a winch. Each device is powered via the battery and a buck converter. The ...
1answer
26 views

### How to interface HCSR04 ultrasonic sensor with ATxmega256A3?

I have to interface HCSR04 with ATXMega256. I am using the TCC0 Timer in Capture mode with setting it to capture pulse width, using Event System Channel 0 source: ...
1answer
46 views

### Is there a minimum voltage necessary for solenoid?

For solenoids or electromagnets, is there a minimum voltage required or necessary? Example, 100mm long iron wrapped with insulated copper.
0answers
19 views

### USBC loading voltage problem

We are trying to get voltage from a DC power supply, it’s connected in series by soldering the wires from the DC power supply to a switch. The other end of the switch is a male USBC connected to a ...
2answers
37 views

### Optocouplers driving MOSFETs in an inverter

For many hours I was trying to simulate in LTspice XVII an optocoupler driver for MOSFETs in an inverter. My project is to build a SMPS with linear voltage stabilizer (I didnt put it on the schematic ...
1answer
32 views

### CD4006 Behavioral model in LTSpice

I want to simulate the behavioral model of CD4006 chip in LTspice. It is a CMOS 18-Stage Static Register. Looking at the Datasheet I see the one stage logic diagram that consist of inverting buffers ...
1answer
26 views

### acs71020 Connecting and reading voltage properly

I am using an ACS71020 3.3V I2C version hooked up to ESP32. I have connected the IC as proposed in the datasheet. Rsense used is 1.8k ohm as proposed in the evaluation board user manual for 230-240 ...
1answer
33 views

### Geometric spreading of an impulse antenna

I am new to radar and curious about the geometric spreading in free space. I set up an air-coupled antenna about a half meter above the ground, with a large PEC on the ground. Then I adjusted the ...
1answer
40 views

### Need Help identify ICs in battery protector PCB

Does anyone recognize these ICs? Manufacturer, model # etc. They are part of a lithium-ion battery protector. Many thanks for your help enter image description here
2answers
41 views

### Is the TC (“terminal count”) output of a 4-bit sync counter (74163) reasonably assumed to be glitch-free?

My gut tells me so, but the proof eludes me. Effectively this output is the AND of all four bits. These four bits go from 0 to 1 at very distinct times, assuming the counter is running at a ...
1answer
78 views

### LTspice not getting exactly -3dB point

Looking to answer another question on this site, to did some math and fired up LTspice to check some values and I am not able to the -3dB point. I found the transfer function to be  H(s) = \cfrac{...
1answer
30 views

### NXP PCA9615 I2C differential buffer - failure on SCL line

I am using the PCA9615 part to extend an I2C bus. The PCA9615 converts I2C to a differential bus. PCA9615 https://www.nxp.com/docs/en/data-sheet/PCA9615.pdf There is a control box and a remote ...
1answer
67 views

### How to enter bootloader on a Embedded Linux System with no keyboard?

I am trying to reflash a microcontroller. An instruction in the manual states that: Power up the owa4x and press the space bar to enter the bootloader prompt Insert the uSD card with the ...
2answers
50 views

### One step-down regulator 24 V to 1V or two step-down regulators with lower steps?

I am trying to design a working principle scheme to step-down the input voltage from 24Vdc ---> different low voltages (1.8 V, 1 V, 1.5 V, 3.3 V with ripples ~ 1%). Could you kindly explain me the ...
0answers
41 views

### Current through resistor in opamp circuit

I have problems calculating the current through the resistors Re, Rr Maybe someone can help me with this, I don't know how to ...
0answers
21 views

### Operate Tablet without Battery while using OTG

First time poster so please correct me if I'm doing something wrong. I have an RCA Voyager III that doesn't seem to charge when I'm using an OTG cable (necessary for our design). I've even stripped a ...
2answers
47 views

### How to connect a few shields correctly?

There are several shields on my PCB: shield on CAN-bus, on RS485, on Ethernet, on ENCODER motor signals. How do I correctly connect all these shields? If I use the star topology, which filters should ...
2answers
52 views

### Equivalent circuit and substitution

Two circuits are equivalent if you provide a certain voltage to the terminals the current through the terminals will be the same and and vice versa; i.e. if you let flow a certain current through the ...
0answers
11 views

### STM32WB55 and transmission of strings over BLE

I have developed a "Medication Device" which will enable elderly people to take their medicines on time. It will memorize all the information such as Name of Medicine and Time to Take Medicine. The ...
1answer
34 views

### TinyFPGA A series board programmer compatibility

Since the programmer writes configurations to the flash of the fpga can I use the TinyFPGA programmer for A series boards on any lcmxo2 chip? Or can I at least use it for the same chip with a ...
3answers
64 views

### Getting a USB PD 3.0 port to output a constant voltage

I am trying to use this AC-DC wall adaptor as a simple constant voltage source to power a compact adjustable DC-DC converter. www.amazon.com/Charger-RAVPower-Adapter-Compatible-MacBook/dp/B07PLR7T1M ...
0answers
46 views

### Phase angle between two sinsoidal currents

I am having trouble solving an example in the book I came up with another solution, anyway the question asked to find the phase angle between two give currents- see attached image what I did I ...

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