EDITED. I found that my supply of 3V was insufficient as there are voltage drops across the transistors. I replaced the 3V supply with 4.5V and the motor ran fine - although now my 3V motor has 2.5V across its terminals (3.3V to 0.8V). I did not think that DC motors exhibited any voltage drop since the current through their coils is constant. What can be done about this? And how would you calculate the voltage fed to the motor ANYWAY? I found it to be 3.3V simply because I measured it.  I have read over the data sheet for the L298 and it seems quite simple to use. Using one side of the chip (i.e. one H-Bridge) set IN1 to 5V and IN2 to ground to conduct from OUT1 to OUT2. Also, to enable the H-Bridge ENA must be 5V. That is all the wiring needed aside from some stabilizing/filter capacitors and flyback diodes.  So, to not mess with all of that I have simply purchased the Sainsmart L298 Driver module. Below is a photograph of the module and I have drawn on it to illustrate the pins that I have wired.   *Note that I have not included the 5V to ENA because (shown towards the bottom left) the board has some jumpers connected so the pin is always 5V.   Also, there is a state switch at the bottom right. From my experiments, and from what I have read, if the button is depressed (closed) then then VCC is tapped and regulated at 5V for the logic circuitry and the 5V (far right of the bottom screw assembly) can be used to power external circuits. If the button is OPEN then VCC is not regulated and you must supply an external 5V supply to this pin for the logic.   Now, my motor is only rated MAX at 3V DC, so obviously I have to leave the switch open and supply the two sources independently.    What I have noticed:  If I have everything wired up exactly as I have shown in the depiction below (but without the motor!) it works fine!   I have put a multimeter across OUT1 or OUT2 to ground as my microcontroller code executes (simply code to run one way then reverse direction), the polarity of the pin changes as expected.   If I place my motor across a 3V supply momentarily - it runs!  If I place the motor leads into OUT1 and OUT2 (after I have verified that the voltage polarity switches) nothing happens. Actually, the indicator LEDs that show direction (that were working prior) no longer light up with the the polarity of IN1 and IN2 changes.   What the heck is happening? Could it be that the board is not supplying the current required to turn the motors? These motors are quite small and the Absolute Max current draw of the L298 is 2A for a single bridge. I checked the datasheet for these motors and they draw 2.2A at stall and 300mA no load.     Here is the schematic for the actual L298 pin soldered to the above board. As you can see, the wiring scheme that I provided above should work just find. OUT1 should conduct to OUT2. The board just includes protection diodes and filter capacitors.
123253
I'm trying to use an  and an Arduino UNO R3 to drive a bipolar stepper motor.   To simplify things, I'm just trying to get a 12v output from either output-1 or output-2 of the l298 (then I can write up the 2nd h-bridge in the l298 the same way and be able to drive both motor coils).  I'm only getting ~130mv from output-1 and 140mv from output-2 (measured between the power supply ground wire and output-1/output-2). The motor is a 12v motor, but I've been able to drive it with an l293 which provides only 6v.  I am getting 5v on the logic supply voltage pin and ~4v on the enable pin (using analogWrite(3, 200) - tried with the enable pin connected to either the analog pin 3 or the digital pin 3 (labeled pwm)).  I have measured supply voltage to be 11.85v (12v power supply).  I have followed the wiring/code from  and  (using same arduino code, but they got it to work, and I can't).  I have tried connecting the Current Sensing A pin to the power supply ground as suggested on the 2nd web page.  I have double checked that I have wired it up the same way. I've tried everything on both web pages and the few other pages I can find about building a circuit with an l298n and an arduino and I'm out of ideas about what to try next.  Is there anything I can do?  Here's a picture of what I built:
22406
I am supposed to come up with some control schemes for the converter before understanding the standard PWM control scheme.   Isn't it just enough if the output of the converter is compared with a fixed reference voltage to drive the output to required voltage level? Although I'm not sure there is a lot more to it, this seems to work pretty well.   I've tried simulating this circuit with L,C and R values from an example.  Schematic:    The required output voltage is 6V. S2 is a voltage controlled switch, controlled by the output of comparator.    V2(green) is the output of comparator and V1(red) is the output of buck converter.
15015
I have two pieces of single-phase fans and they are literally the same, it is ac motor and whenever I rotate it manually it produce voltage about 160-190vac. I just get the idea that it can be an ac generator, but the problem is when I connect it to 110v-220v cellphone charger, the charger is not working, the voltage drops and the generator seems to run from the voltage itself, I search it and the answer is the backfeeding. I also connect the generator to christmas lights and there is no problem maybe because it has resistors, I also conect Led bulb using an adaptor 110v-220v and the led is blinking(it should not be) and everytime it blinks the generator get a shock, it seems to get backfeed. The other problem is I connect these 2 ac fans and I rotate it to be a generator(160v-190v each) but they seem to be run from the voltage themselves. I had this idea to use a full rectifier, inverter or somewhat to make them a working generator with a stable of 220vac even if using. My ideas/plans (in order):  To stop the backfeed of the generator when using. If there is no possible way to do that then using an inverter is the last option. If ac-dc is the best way then i'll connect dc's from positive to negative, making dc volts step up then convert it to 220v ac. AC-DC-AC in short If no. 2 didn't work, then i'll suppose to make an inverter for each generator making them ac-dc-ac and avr for each to stabilize their voltage.  Please help me guys, I need to make it possible. Another thing I recently know, is it possible to put a ground wire to a single-phase generator to stop getting backfeed instead of transfer switch ? The picture is the single phase motor.
11076
I have a  (BB) and want to connect the analog output of a motor controller to it. The motor controller creates an output in the range of -4V to +4V and the BB anlog inputs only accept voltages between 0V to 1.8V (digital  pins run at 3.3V). I only have a comparably small limited space of perfboard available, but 4 motors to monitor. I can provide 5V and 3.3V supply and 1.8V ref Voltage. Here are the options I found so far:   Make an op-Amp circuit to convert [-4..4] to [0..1.8]. Probably a nice way, because I could use directly the BB-ADCs, but I am not to confident with these circuits (I found this ) and I would need one for every input which seems to be to many parts/space. Use an ADC and connect it via I2C: The  seems to provide exactly what I want. Single 5V supply, analog input range between [-5..+5] and I2C interface. I would really like to use this one, the only problem I have is that according to the data sheet digital high is seen as 0.7*Vdd = 3.5V. I do not now if 3.3V would be detected correctly (anyone has experience with that?). Pulling up to 5V is not possible as the BB is not 5V tolerable. The  is basically the same as the Max127 but with SPI-interface. There the data sheet states the digit high threshold is 2.4V. I know that the I2C slave only pulls down. How does it work with spi, because the data sheet mentions digital outputs voltages (which are Vdd)? Lose some resolution and only use the output range from [0..4]V. That gives a larger variety of possible unipolar ADCs, but most of them have the same limitation with 0.7*Vdd for digital high signals. As in 4. But use ADCs with 3.3V supply voltage which have a range of [0..5], but I could not find any with 4+ channels.    I believe that I somehow going in circles. Does someone know a viable solutions or how to address the mentioned problems of (at least) one of the above described?  I would generally prefer through hole parts (as it's perfboard) but I could probably get some small breakout boards for SMD-devices as well.
65384
I want to make a power DC supply with voltage rating 0-200V. I want it to be a variable power supply with voltage from 1V to 200v. What should be my approach?
19453
When measuring the AC voltage across a DC battery (CR2032), and I am getting 6v. The DC voltage across it is 3.01 volts. I also tested on a 9 volt battery; again the same thing. I am reading about 20 v AC and 10v DC. I am using MASTECH MAS830L multi meter. I also used another multimeter, and I get the same result.  When I am putting the multimeter probes in the same polarity with the battery, I am getting the AC voltage, but none if I put the probes in reverse polarity.  Why is this happening?
15473
I'm trying to drive a 12v (14W) solenoid and have problems figuring out the components for the driving circuit.  The solenoid draws about 1.166A and the MCU is being operated at 3.3V.  I've seen many driving circuits and they all look something like this:         &ndash; Schematic created using   My questions:   What datasheet parameters should I look for when designing this circuit? Is the IRF530PBF-ND a suitable MOSFET for driving this solenoid?    Also, how do I calculate R1's value?  I don't want to blindingly copy a circuit that may or may not work, I want to understand it.  Thank you so much in advance!
64379
Looking for a simple design to convert from 4-20mA signals to 0-3V3, I'm thinkin about configuration shown at picture attached.   And I would like to discuss its suitability.  It is based on: - A follower configuration for a Rail-to-Rail OpAmp, powered  at 3V3. - A 165Ohm resistor to get, 3V3 at 20mA, and 0V66 at 4mA.  What do you think about?  It is any improvement I can do? Or it would be better to work with another more precise configuration?   It is thought for a low power applications (&lt;5V), but it would like to know if it could work with 4-20mA transmitters powered at 24V too.
10727
What would be the least expensive way to boost a DC voltage?   The aim is to convert 1.2&nbsp;V/1.5&nbsp;V (from an AA/AAA cell) to 3.3&nbsp;V to power a small 8-bit microprocessor, like Atmel ATtiny45 or ATtiny2313, and also (if possible) 6&nbsp;V to power a buzzer.  Also, what would be the maximum current one could draw safely from an alkaline battery, after boosting it to 3.3&nbsp;V/6&nbsp;V?  Finally, how I could compute the duration for which the alkaline battery would last, given a certain consumption?
39949
I want to supply constant voltage to my LED's but the supply varies from 3.7V to 4.2V (Li-ion battery). I cannot use 3.3V voltage regulator as it will need at least 4.3V voltage at the input but my battery can supply only 4.2V max. so is there any other way I can supply regulated 3.3V to my LED.   RGB LED = 3.3V, 60mA Battery = 3.7V - 4.2V, 3000mA Number of LEDs = 24 The LED's are connected in parallel
78761
I just purchased .  I'll be installing it in my RV.  Current will be supplied by a 12VDC to 120VAC, 3000W inverter.  I'll be using Single-Pole Type BR breakers.  Here's a picture of the box:    My current understanding is that I must install a grounding bar to the box.  This is my current understanding of how to connect the breaker to the main supply.:    Here is my understanding of how I would wire in new circuits:    Does this look right?  I would really appreciate your help -- I've been beating myself over the head about this.
30594
What will happen if motor requirement due to more load is high(lets say 5A) and we limit current with current limiting circuit to lets say 2A. what will happen.. will it work without anything getting damaged?If not what should i do? Thanks..
96004
I'm hooking up a small DC motor to an arduino using an NPN transistor using the following diagrams I found online:       The circuit works, and I'm successfully able to make the motor run.  Now, I'm seeking to understand why it works the way it does.  In particular, I'd like to understand:     Why are the diode and capacitor hooked up in parallel to the motor?  What role do they serve here?   Why is a resistor needed between the transistor and the digital PWM pin on the arduino?  Would it be safe to run the circuit without it?
20192
I would like to connect an electric toothbrush motor (Braun Oral-B Type 4729) directly to external power supply. So far I have been trying at least 3 different DC power supply unit with appropriate voltage (1-5 V) but nothing happened. However motor works perfectly fine when connected just to a regular battery (AA, 1.5V)...what is happening? The only guess I have is some impedance mismatch between the source and the motor...can anyone confirm this and/or provide any solution how to connect this motor to regular DC power unit? Thank you very much!
12988
Sorry if this is a stupid question, but I am mainly working with 5V PIC circuits and now want to integrate a component (nRF24l01+) that needs a 3.3V supply.  As I have a box full of ~7V wall-warts, I normally use a 7805 or similar LDO regulator to power the circuit. Now I want to also get 3.3V without using a separate external supply.  I'm looking for guidance on the "right" way to do this. I think the options are:   Use a voltage divider on the output of my 5V regulator to get 3.3V Use a 3.3V LDO regulator fed directly from the 7V wall-wart   Use the output of the 5V regulator as input to a 3.3V regulator   I can see that all of these would work (would they?) and that option 3 seems to waste least power, but I don't know what gotchas might arise by chaining two regulators like this.  What things do I need to consider when making this choice?
22045
Have a look at the diagram above.  It shows an op-amp with negative feedback.  Ignoring the feedback loop for now, the voltage (pressure) coming from the 5V battery, acting on the inverting pin, should amount to 5V.  Now, I understand that the feedback loop is adjusting the voltage on the inverting pin to make it equal to the reference (non-inverting) pin or 3.3V and you can clearly see that the output is producing a negative voltage to achieve this.  I also understand that the input pins have a very high impedance.  What's confusing me is how it actually does this (considering my rudimentary knowledge of electronics).  I considered that the output was sinking some of the current produced (by the battery) to alleviate the pressure on the input pin and bring it down to 3.3V, but clearly that isn't the case (since the 1 ohm resistor is passing 5A).  So, I'm struggling to understand how 5V of pressure from the battery results in 3.3V on the input pin.  I'd appreciate it if somebody could explain this in an intuitive way.  Much Appreciated.  Edit:  Many thanks for your all your comments and insights.  The circuit itself is a distraction.  At the heart of this is my attempt to understand op-amp and negative feedback behaviour.  I wanted to understand the following:  a) if you could apply an input voltage to the op-amp that was different to the reference voltage (more specifically that you have voltage "pressure" acting on the input pin that is higher than the reference pin). This also assumes that you have some other input other than the feedback loop.  b) if a is true (and assuming that the op-amp adjusts its output to equalize the voltage on both pins) how is this achieved?  Clearly the feedback loop plays a part and the only thing I could think of was that the output was sinking current to take the pressure off the input pin and thus explain the voltage drop between the between the higher voltage source and the voltage appearing at the input pin.  Incidentally, the question would still stand even if you had a resistor between the source voltage and the feedback loop/input pin junction.  A better circuit example is shown below (taken from ):    But with V1 set to some voltage other than 0V.  Final Edit (Promise!):  From the electronics tutorial article linked above:  "This negative feedback results in the inverting input terminal having a different signal on it than the actual input voltage as it will be the sum of the input voltage plus the negative feedback voltage giving it the label or term of a Summing Point."  This is exactly where my confusion lies.  As I understand it voltage is simply pressure exerted measured with respect to some reference point (usually ground).  What the paragraph above is suggesting is that at the "summing point" there's a change in voltage (pressure) because of the addition of the feedback voltage.  Intuitively, I'm thinking that the output pin "sinks" some current to reduce the voltage at the summing point.  But that sinking of current would reduce Iin (since no current flows through the inverting pin).  The result would seem to be that Vin drops.  But is this the case?
41588
So I found this 9V 1A AC power supply laying around and decided to make a DC source.  I rectified and added a capacitor to make things a bit even. After adding a capacitor my voltage boosted from 9V to 14V. Can somebody explain why this happened for me? (maybe this has something to do with frequency?) According to theoretical graph I should get aprox the same voltage even after adding the capacitor. And voltage varies depending on how much capacity the capacitor has (aprox. from 12-16V). Maybe there's some sort of equation to determine the actual output voltage depending on caps? It would be great to get 12V out of this thing.   P.S.: Personally I find this boost weird because this circuit doesn't have any switches and coils to boost the voltage, so I need an explanation, thank you in advance!