Tagged Questions
2
votes
6answers
90 views
Switch transistor with a low voltage and current
I'm designing a circuit that will use a combination of switches and resistors to allow a microcontroller to identify which switch was pressed based on the voltage read and perform a switch-specific ...
0
votes
0answers
71 views
Is it safe to use a Relay to control my room lights with a microcontroller?
Firstly, I would just like to state that I'm a complete n00b to electrical engineering.
I'm thinking of controlling my room lights with a microcontroller.
The way I'm planning to do it is by placing ...
0
votes
2answers
167 views
Transistors never work for me
TOday, I have built an LED cube. I put it all together, arduino, mess of wires and all, and it doesn't work. Fiddling with it a little bit, I find that if I short certain wires to ground, the LED's ...
2
votes
2answers
171 views
What can I do as a student to be a better candidate for a hardware design job? [closed]
If you were looking to hire a student still in school for an internship position at a high-tech company (say, Microsoft, Apple, or Google) for hardware design. What kind of skills would you be looking ...
1
vote
3answers
302 views
Any way to use N-channel mosfet in P-channel configuration?
In my application, I need the HIGH signal to turn a device OFF and vice versa. Clearly, this is P-mosfet configuration. However, I only N-mosfet on hand.
Is there any clever way to utilize N-mosfet to ...
2
votes
2answers
187 views
LED tachometer with PIC MCU (requires more current)
I've been working on an LED tachometer that will be installed on an open wheel race car. After putting the order through for the PCB I re-calculated the current draw and turns out the PIC's (16F877A) ...
1
vote
1answer
164 views
Accelerometer and Transistor
Here is my program, I want to:
The microcontroller, Arduino UNO R3 sends 3.3V to the sensor, Accelerometer, MMA7361
The sensor turns on and send signal to the microcontroller.
When I move the sensor ...
1
vote
1answer
222 views
Alternative to optocoupler? Other switching devices?
I have a part that classifies what kind of power I get on ethernet by presenting different loads. For example, the part needs to have a 100 Ohm resistor across two of its pins, and the part will ...
7
votes
1answer
176 views
Current flow priorities in PSU / PSU review
Being an electronics hobbyist, I'm having quite a challenge to design a PSU, which must run both on batteries (during the night time) as well as on Solar energy (daytime). The device is intend to run ...
2
votes
2answers
1k views
Driving a large 7 segment display using a micro-controller
I need to drive a large seven segment display (segment length is a about 2 inches) using a micro-controller (PIC 16F877). I've driven normal seven segments directly from PICs without issues, but I ...
3
votes
2answers
1k views
Arduino/Atmega with TIP120/121/122 transistors: base current question
I am learning about transistors, and can't seem to find the answer to a few questions which are stumping me. I will be referring to the TIP120/121/122 Darlington Transistor.
As I understand ...
1
vote
1answer
220 views
Backup battery tester circuit
I am attempting to read the voltage on a backup battery on an Arduino. To that end, I used the circuit Olin Lathrop offered in answer to this question. I am powering the Arduino with 5V, and the ...
12
votes
2answers
1k views
Selecting a MOSFET for driving load from logic
I'm looking to drive a magnetic door lock from an Arduino. I've found a question about driving a solenoid from an Arduino, which includes a circuit that looks perfect for this kind of situtation:
...
4
votes
2answers
1k views
Driving Solenoids from Arduino
I was wondering what the best way to run a solenoid would be from an Arduino board. I was thinking about using a MOSFET that runs into a relay to turn on the solenoid but am not sure how to go about ...
1
vote
3answers
312 views
Electronically switched decade resistance box design
I'd like to design a decade resistance box that uses a microcontroller to control the resistance.
Would it be possible to switch between different valued resistors using transistors? (or another ...
2
votes
1answer
1k views
Transistor current limiter, microcontroller controlled?
I've come across a few transistor current limiter schematics, similar to this one:
However, I am not entirely sure how I could implement microcontroller functionality to control this. I think ...
5
votes
2answers
730 views
Transistors: why are resistors needed?
I have a solid state relay which needs at least 3V to activate, and I need to toggle with a 2.3V output from a microcontroller. I've also got a 6V 1A power supply which I can use to power the relay.
...
4
votes
4answers
1k views
Is this a proper use of a PNP transistor?
I'm attempting to use a transistor to switch on and off an SSR, which in turns switches on and off a solenoid. I originally used an NPN transistor (2N222), but this caused problems when the MCU ...
2
votes
1answer
402 views
Voltage controlled voltage source
I am designing a high powered LED driver controlled by a microcontroller.
Now it would be very easy to make a constant current limiter so I don't burn out my LED. I have a bunch of LM317's and ...
13
votes
4answers
4k views
When is a MOSFET more appropriate as a switch than a BJT?
In my experimentation, I've used only BJTs as switches (for turning on and off things like LEDs and such) for my MCU outputs. I've been repeatedly told, however, that N-channel enhancement-mode ...
2
votes
1answer
481 views
How to switch/power a 13x13 LED Matrix?
Hey all - I have an AVR project in mind that will require a 13 by 13 LED matrix of bright white LEDs. I'll be wiring up my own matrix to do this (not using premade 8x8's). I plan on using some shift ...
7
votes
3answers
4k views
How to pick a switching transistor to drive LEDs? Or, how to read a transistor data sheet?
I'm going to be driving a bank of 20-25 LEDs from a single output of a PIC micro. Obviously, I need a transistor, because that's going to be somewhere in the vicinity of 400 mA (the LEDs are speced at ...
