I am trying to connect the MMA5452Q accelerometer to arduino on 5V (later it will be substituted with attiny85, hence the 5V voltage). It works just fine when i supply arduino's 3.3V. When i try the 5V supply and split it with resistors (R1, R2, R3) the accelerometer does not work any more. I measured the voltage of the circuit. It is 1.1V but MMA5452Q requires 1.6-3.3V. I was trying different combinations but i am afraid that doing it blindly at some point I will just burn the chip. What is going on here? Could anyone tell me how to connect it so the voltage maches? (And how to calculate this - so I dont need to ask every time :)  )  P.S. R5 and R4 are pull ups required by accelerometer's documentation. Works when the circuit is powered with 3.3V  P.S.S. I am not an electrical engineer. I am hoping that this question is not terribly stupid.         &ndash; Schematic created using
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When would you use a voltage regulator vs a resistor voltage divider?  Are there any uses for which a resistor divider is particularly bad?
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Automotive Circuit requirement:   If input pin is connected to Battery(T87 line), the output of the circuit shall provide a output voltage of 5V to ADC pin of microcontroller, if the input pin is connected to GND, the output of the circuit shall provide a output voltage of 0V to ADC pin of microcontroller and if the input pin is left floating, the output of the circuit shall provide a output voltage of 2.5V to ADC pin of microcontroller.   The battery voltage in load dump condition could be up to 60V, but in normal operation without any fault condition, it would be up to 32V.  Would a simple voltage divider (with a pull-up to 5V) with a blocking diode be enough? Any other ideas? What parameters of the ADC of the microcontroller should be considered? Injection current into the uC- ADC pin would be critical, right? How do I find out the voltage thresholds? Also, what are the parameters of the Schottky diode that I should look to select? The diode would decouple the input pin from the centre tap of the voltage divider, because in case the input pin is connected to battery, the injection current into the uC ADC pin would be too high.  I have used a switching diode, since it was already available in the Bill of Materials.
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Different from the best answer of this one:  But well, I'm also an electronics noob ^.^  Recently I bought the official Arduino starter kit and played around with the common cathode RGB LED that came with this kit. In the project book, the instructions for the colour mixing lamp is to use separate 220ohm resistor for each of the RGB legs. But I thought, why can't I put the resistor on just the cathode of the LED?   I tried that by plugging the LED into the breadboard and connecting the cathode through a 220ohm resistor to the ground of Arduino UNO. When I touched any one of the R, G or B anode legs with a jumper wire connected to +5V, the respective colour lights up alright. However, when I bridge the G and B pins together, only the green LED lights up. When I bridge all three anodes together, only the red LED lights up. But if I connect the anodes to +5V through their separate 220ohm resistors(according to the instruction), the colours will combine.   Why is it so?
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I'm trying to build a 555 timer with a 50% duty cycle.  I followed the instructions given  (pg 12).  I used a 470 microfarad capacitor, 150 ohm resistor and a kohm resistor. The output voltage is always low.  I've attached an image of my current circuit and would appreciate it if someone could pinpoint what I'm doing wrong.
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I want to understand the way this circuit works. The following are diagrams of the transmitter and receiver of a wireless iPod charging circuit. I have added a link to the instructable that describes this project. From what I have understood, the transmitter takes the DC input voltage,and turns it into an oscillating signal that can be transferred to the receiver circuit through the inductor. The recieving circuit then rectifies, filters and regulates this signal to give DC output?  Is that how this is working?  Also, are the resistors in the receiver circuit put there for the female USB? Why? Also when I bought the diodes for the transmitter circuit, I could only get 1 UF4007 and the other is a 1N4001. Will that affect the functioning of the circuit?  Thank you for your time!   This is the transmitter circuit.   This is the receiver circuit.
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In the link below, this circuit I found is what I needed. Only the length of the pulse and the delay are not what I want.  When I want just 0.5sec before pin 3 is up and the pulse duration I want is also 0.5sec, can someone tell me how big my resistors and capacitors must be? Or can someone tell me how I can calculate this?  My source power is 16 Volts I have already found 555 timers that can operate with 16 Volts, so thats not the problem.  When someone has another idea with two 555-timers, or something else that does the same, it's also OK.  Thanks
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For some reason whenever I play with a multimeter it always gives me results I never expect. In this case I am attempting to measure the current of a AA battery. I have the multimeter set to 10A on the dial and connecting red to the negative end of the battery and black to the positive end, giving me a reading of about +6.8. However if I switch the dial to 200mA with the same connections the reading goes off the scale but with a negative number, -1. Is this behavior normal? It is a digital Southwire 10030S multimeter.  After testing with an analog meter putting negative to negative and vise versa I get a positive reading of about 5 amps though the gauge gets stuck usually. It says PRIME Cleveland Ohio on the back.    Looks like I had the fuses in the back swapped with each other and after correcting it is now matching the readings of the analog meter :D
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I have 12V, Use these 12V to power a device (that has a 12V output signal) and to power a 7805. After the 7805 there is a pic microcontroller where I would have to connect the output from my device. I was thinking of having 2 resistors in a 3/1 ratio in order to have about 4V at the pin of the pic. Can this be done, given that the ground is common, or will it give some sort of problem with the lm7805?
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I have been looking around for an easy way to convert 12V to 5V. I have seen some people saying that a simple resistor is all that is needed.  $$ Volts = Ohms \cdot Amps $$ $$ Amps  = \frac{Volts}{Ohms} $$ $$Ohms  = \frac{Volts}{Amps}$$  So applying a resistor will diminish the voltage of the circuit. That should mean that an appropriately sized resistor could simply be placed in the path of a 12V circuit, converting it to 5v.   If this is the case how would one reduce amps? Would series vs parallel make a difference in this area?   I have seen designs that include a regulator IC and some capacitors, but if a simple resistor/fuse/diode setup will do the trick, I would really prefer that.
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Is there any IC that interfaces any 3.3V Input/Output to 5V Output/Input? I need it primarily for an Arduino Due but if there any bidirectional IC that works like that it would be great.  Some people advised me to use the SN74AHC125 and CD4050 ICs, but I don't understand how they work or how to interface with them.
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I am attaching a motor to an ATmega32 chip. I want to build an H-bridge but before doing that, I want to control the motor using the chip. I bought few NPN Transistors from RadioShack. I have 5V running though the breadboard. I attached Vcc to the Collector, Base to the Pin, and Emitter to the motor. And other wire of motor is hooked up to Ground. Unfortunately, the power coming out of the transistor is too low, the motor is barely moving (As opposed to when I hook up my motor straight to 5V). What is wrong? Do I need a different transistor or is my setup wrong? If it is the transistor, can you please recommend the right one, I am not too good at those.
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What's a good way to reduce the output from a 9V battery to the 1.8V to 5V required by an ATmega328 controller? The context is a small robotics platform with low power requirements (very slow movement).
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I want to run a micro-controller from a 1S lipo through a 3V linear regulator. I need to measure the battery voltage however. The problem with using a voltage divider is that it would drain the battery over time which may or may not have protection circuitry built in. Since the AVR I'm using has a recommended input impedance of no higher than 10K I can't make the divider too large either.  Can anyone suggest a solution that would allow me to monitor this voltage without killing an unprotected battery over a couple of months? The circuit might enter deep sleep mode for an extended period meaning a voltage divider solution would consume the most power.    I ended up using both Hanno and Andy's solution. Thanks for all the input. Can only choose one answer unfortunately.
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I'm teaching myself EE while designing a 12V DC battery monitor. I'm using a pair of Hall-effect sensors to track charge &amp; load current and looking for the best way to measure the voltage. [An ATmega32u4 will take successive reads with the ADC, compute a 1-second average, and pass that up over USB for logging and analysis.]  The issue of error with ADC really has me spooked. It is essential that I produce meaningful data. There's so many error sources&mdash;both in my circuit and in the ADC&mdash;that it feels like playing wack-a-mole in the dark. I'm reading lots about calibrating the ADC's reference, but the first step is to pick a method for scaling the input.  My voltage window is 10-15V, specifically a range from 10.5V to 14.4V (3.9V). I came up with two approaches that (hopefully) do what I want:   A 10V Zener diode on the inverting input of a differential op-amp. Rejecting 10V, my range becomes 0.5V to 4.4V (3.9V) and uses nearly the whole range of my ADC.  A 20k : 10k voltage divider. Scaled down 3x, my range becomes 3.5V to 4.8V (1.3V)   I wanted to prove to myself which method would render the best granularity. Since I can also obtain 12-bit accuracy by adding four reads and shifting the result, I compared four possibilities: (assuming ADC ref is 5.0V)   method 1, 0.5-4.4V @10-bit is 800 steps: 4.88mV/step [#3] method 1, 0.5-4.4V @12-bit is 3606 steps: 1.22mV/step [#1] method 2, 3.5-4.8V @10-bit is 266 steps: 14.65mV/step [#4] method 2, 3.5-4.8V @12-bit is 1065 steps: 3.66mV/step [#2]   My question is, do my mV/step figures tell the whole story, or is there some kind of downside to #2 that I'm not seeing?
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I am building a battery powered device. Almost all of my logic is running at 3.3v, although I do have a 5v supply for a few hobby servos.  I want to measure the battery voltage, but I can't do so directly with the ADC on my controller because the battery voltage (depending on the cell count of the lithium polymer battery that the user connects to the device) can vary between 6 and 36 volts. (My 5V and 3.3V supplies are fine with this input variation already.) The ADC can't measure anything above its supply voltage.  Obviously I need some sort of amplifier with a fractional gain, about 1/12 or so. Should I just use a simple voltage divider? How do I decide what values to use? Maximizing sleep-mode battery life is a concern, so that votes for using large values. What constrains how large those values can be? (The input impedance of the ADC, right?)  Am I better off using some sort of opamp amplifier circuit for some reason?  What's the usual solution here?
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I want to connect the output from the audio jack of an iPhone to an Arduino.  What voltage range can I expect to see on the audio lines from the iPhone? I assume that turning the volume up on the phone will produce a large AC voltage, but how large does it go up to?  I want to make sure that it wont exceed the voltage level that an Arduino can read on its input pins. Will I need to provide any circuitry between the iPhone and the Arduino?
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This might be old news in a half a decade or two but by today's means, I am referring to electronic prototypes and designs which would draw in a μA (uA) and even nA range of current.  Some recent MCUs, such as SAMD21 that I am using atm are armed with internal clocks such as ,always on, Ultra Low Power Internal 32kHz RC Oscillators which would draw only 125nA, and the whole microcontroller is capable of consuming only 6.2μA on STANDBY mode with a live RTC.   In these type of quiescent current and power consumption levels the smallest limitations in the internal machinery of bench measurement devices such as multimeters and oscilloscopes could add a fair bit of error to the overall measurement or even measure a flat out wrong value in situations like a different relay kicking in when changing the resolution from 6 to 8 decimal places accuracy on your multimeter.   What is the most precise method of measuring the overall quiescent current/power consumption for such applications?     Update:  As I mentioned in one of the replies, measuring low currents is hard but very possible, however, making conclusions on the integrated amount of current consumption to come up with numbers for the realistic over all power consumption is more what I had in mind.  I have bumped into some solutions such as , however the wide range in this application note is only limited to the max of 200uA and in my case, my max current can rise to milliamps when my radio is transmitting and could drop to as low as 3uA when the whole system goes to sleep.