# All Questions

11 views

### Easy circuit question

Find the current IA in the circuit in Figure: http://i.stack.imgur.com/AcydV.png so far I have started the problem by combing the 1kohm and 2 kohm to create a 2/3 resistance. I am currently stuck ...
10 views

### Understanding pull-up resistors and the 7489 memory chip

I have been learning about the 7489 memory chip. I had two of these that turned out to be broken (see here for previous question on this). I got more and I have finally gotten everything to work. ...
25 views

### Are there any open / unrestricted radio frequencies that are free for any use?

The only 'free radio frequency' that I could think of are the HAM radio bands. But they really aren't free, for they are regulated by laws that require you to hold a license, restrict what purpose you ...
20 views

### Transistor behavior in Current Limiting Circuit

I have a circuit that I think will work, but I am worried that if I am overlooking or misunderstanding something about transistors in current limiting applications. The following is nothing original. ...
18 views

### What are the underlying physical principles of a constant current power source?

I´m currently looking for a led driver to drive a 34,25 W High-Power LED at 38.06 V / 900 mA. Browsing trough various online shops i found a constant current source and i don`t get how it works. The ...
11 views

### Semiconductor Experiments and Theory Textbook Recommendation

What are good textbooks that talk about semiconductor theory and the experiments that support the theory? Experiments that agree with both the conclusions of semiconductor theory, and with the ...
9 views

### 8051 Microcontrollers question about TH0/TLO flag values

Welcome all, I know, that i'm in a right place to ask about something which is related to microcontrolers programming area. I'd like to know how can I calculate TL0 values. For example, when we have ...
16 views

### Dual output with Center Tap transformer

I have a transformer with dual input 115v and dual output 9v and rating power 1.15va. My goal is to connect it in parallel to produce single input 115v, single output 9v and rating power 2.3va. The ...
21 views

### Bundle phone lines to create one cable

Could the phone company use its bundled pairs to create a single wire like Cable and run everything over it instead of using them for individual lines? I know they would have to change out there ...
15 views

### How to pick good LED modules among the many low quality ones?

I would like to build a replacement for a 300W halogen using multiple LEDs. Using the rule 4:1 to be safe (75 lm/W vs 19 lm/W), I need a total LED power of 75W, that means two or three 100W LED ...
13 views

### Compare numbers using flag registers

Suppose I have a four bit number. How Will I check whether the number is greater than or equal to zero logically by using flag registers? I can check if the number is equal to zero or not by Or ing ...
63 views

### Lower than 0.7-0.6V voltage drop on sillicon diodes

I am trying to understand how voltage drop happens. From what I know, there should be about 0.7-0.6V drop across a silicon diode. This is exactly what happens when I remove the LED from this ...
21 views

### Interfacing to a Microprocessor Bus without an 8255

There are 32 doors in a building each having a sensor attached with it. Each door outputs a signal 1 if it is open and O if closed. I want to design a pc based system to display the condition of each ...
28 views

### Measurement of power dissipation in a resistance

In the above figure (step up transformer), We can calculate $V_s$ using $\frac{V_s}{V_p}=\frac{N_s}{N_p}$ and $V_s=50 V$ So, power dissipated in the resistance, $P=\frac{V_s^2}{R}=2500 W$ ...
47 views

### Designing a 8 bit ALU

I have started designing a 4 bit Arithmetic and logic unit. The sample image is as follows: The function Table: My question is: Is it possible to design an 8 bit ALU having the same ...
60 views

### adc connected to dac [on hold]

I wish to connect adc directly to dac so that I can transmit audio as digital pulse's , I thus bought these (Analog RCA L/R Audio Converter Adapter to Digital Optical Coaxial Toslink) AND (Digital ...
35 views

### bulk micromachining Question [on hold]

Could anyone give me any hint on how to answer this question?
30 views

### Two-port circuit analysis. Voltage gain

I am trying to find the general equations for the voltage gain(Not sure if it is the write word for it). My textbook offers an derived equation but not the procedure. I would appreciate it if ...
58 views

### Advantages of filtering signals using analog or digital methods?

In my understanding, it seems that there are, broadly speaking, two primary ways in which signals are filtered for analysis by computers, which are software-side filters and hardware-side filters ...
50 views

### What is an appropriate switch for usage in a residential, low-voltage, DC lighting system? [on hold]

I'm in the process of designing a 24VDC LED lighting system for a small 600sqft cabin. The biggest issue I'm having is that I can't seem to find any residential light switches rated for 24VDC. ...
19 views

### Relationship between two Alternators with different frequencies and different voltages [on hold]

A detailed relationship between two alternators having different frequencies and different voltages, with mathematical equations to support.
33 views

### Using the ST-LINK Utility to configure the RTC to current time

What I was doing I am using a STM32 microcontroller and for my project I need to be able to send data at specific times of the day (say, at 11am and 2pm). The microcontroller needs to know what time ...
30 views

### DC motor not working

My circuit is not working as expected. Only one motor is working. Every element is well soldered and well connected except one of the resistors and replaced it with a different resistance. So does it ...
13 views

### In HDB3, does a 1 have opposite polarity to the last 1, or to the last V?

I am trying to understand HDB3, and in particular trying to find out whether the picture below which shows the encoding of a bitstring in HDB3 is correct or not: From what I understand, a ...
36 views

### Externally controlled RFID Tag

I have a project requirement to use open protocol RFID tags to control doors handling of a light rail train (also called a tram in Europe). The application must sync and control 2 different doors: one ...
68 views

### Where do these grounding wires go?

In the following schematic the two Vss pins where are supposed to be the grounding pins don't connect to anything. Does this mean that the circuit is self-grounding (if that's even a thing)? I'm ...
62 views

### What is the schematic symbol for resettable fuses?

I have seen symbols for one shot fuses and circuit breakers, but not for resettable fuses that reset themselves when the fault goes away. What is the recommendation of the symbol to use?
24 views

### Intermediate Frequency in transceiver?

When I learn the transmitter and receiver architecture? They have each own heterondyne architecture they use intermediate frequency to upconvert to higher frequency or downconvert to lower frequency? ...
25 views

### Measuring RF and heterodyned frequencies

I have a question about RF measurement techniques. The partial schematic above is the front end of an AM radio receiver kit. I have assembled the kit. The kit manual states, Transistor Q7 not ...
26 views

### question on “Intercom” circuit I am planing to build

I am using Voice Record Module to save messages and then play them to one from selected outputs ...some kind of weird intercom system. My OA is LM386 [can only do 2 links but I'll post image relevant ...
40 views

### What does J1, J2 and J3 represent on a Schematic?

I'm looking at this schematic for the TSL1401 line scan camera module and trying to understand what the various pins do. I understand what the labels SI, CLK, AO and Vdd mean but I'm totally lost when ...
23 views

### Value and type of unidentified Diode [on hold]

I need to know the value of a component for a PLC monitoring ckt. Please help me.
49 views

### SCR drop voltage

unfortunately there is a voltage drop for the SCR , as I used an opto with a single SCR , when I checked the open anode cathode voltage without any load it was about 5V instead of 12 volts, when I add ...
20 views

### Convert byte by byte CRC-15 to table driven

I am attempting to convert a byte by byte CRC to a table driven method for speed, and am having issues with that. The provided information for the CRC is: Polynomial (\\$x^{15} + x^{14} + x^{10} + ...
27 views

### variable dual contact circuit needed [on hold]

Looking for a circuit that will toggle between 2 switches using a potentiometer. I've found similar circuits for video game (called "auto-fire" or "autofire" circuits), but that only involves 1 ...
36 views

### How to match impedance when driving 75ohm differential video amp with single ended RS-170 video output?

I am trying to feed RS-170 video signal from a single ended amp to a differential 75 ohms video amp. When I connected RS-170 signal to + of the differential and RS-170 return to - of differential, ...
49 views

### Programming an electric meter based on 8086(asm) [on hold]

I need to write a program for this schematic, but my assembler skill is bad. Can somebody give me any tips? I read emu8086's tutorial, but still I cant figure out what to write. It is needed for my ...
59 views

### MPLAB 8.9 won't launch

I am running windows 7 professional 64-bit and up until this week was running MPLAB 8.92 IDE. Now I get a brief look at the splash screen and the IDE refuses to launch. I downloaded and ran the ...
68 views

### Why we can't use AHB in the Cortex M0 MCU?

I found coretex M0 MCU module's bus interface has not HBUSREQ and HGRANT, and HRESP when i trying to implement with AHB Bus. Is there any way to use AHB not AHB_lite. I can't use multi-layer ...
28 views

### RC Servos' potentiometer model/information [on hold]

I have a few disassembled RC Hobby Servos lying around, and started using their parts for different projects. I've become especially interested in the mechanical characteristics of their feedback ...
42 views

### Continuous-conversion vs Single-Conversion mode

I am working with an LSM9DS1 9DOF IMU and was wondering about some of the choices about operating the magnetometer. This is my first time working with an IMU, so I am having some trouble understanding ...
35 views

### How do charge controllers work?

I am creating a small wind turbine, I will be using a stepper as a low-efficiency generator. I have found off-the-shelf "wind charge controllers" but would rather roll my own because I would enjoy the ...
63 views

### Effective resistance seen by capacitor

I needed to find time constant of the above circuit. I guess we should first draw small signal analysis. The book found time constant as (RD+RL)*Cc. It says that we can find time constant using ...
70 views

### Using an array of resistors to give priority on a bus

I remember that the ZX Spectrum used an array of resistors to let the output from one chip override the output from another chip (on a bus) when both had the ¬oe pulled low. ...
207 views

### What does this symbol refer to?

What is the symbol that is below the C1 capacitor and R1 resistor. Is it the symbol of grounding?
59 views

### INA155 reference pin not working

To test the INA 155 I gave a sine wave of amplitude 0.2 V p-p 100Hz. It was operated at 5 V single supply. The reference pin was connected to 2.5 V from an op amp buffer. There seems to be no offset ...
888 views

### Why are infrared LEDs used in optocouplers?

I read that optocouplers and optotriacs use infrared LEDs with infrared sensitive transistors. What is the idea behind using IR frequency but not visible light freq. LEDs inside a completely closed ...
48 views

### Measuring state of charge of a non rechargeable CR123A lithium battery

Is there a method (voltage, resistance, other...) of measuring leftover charge in a non rechargeable lithium battery? Background: I'm trying to get a general overview of power consumption for few ...