I am building a 4 leg robot with a Raspberry Pi and 8 servos ().  Currently I have a a 6 V 3A power supply powering the servos through a 5V 5A buck converter and a 5V 2A power supply for the Raspberry Pi.   This set up works great but I would like to lessen the weight on the robot by using one power supply to power both components. I'm new to electrical things and was wondering how do I determine what the power requirements are to power all the servos and raspberry pi with one battery? Do I just need to increase the amps?
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Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?  Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.
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Is there a tool to print the power supply information, such as brand/model name and maximum (supported) output voltage? I need to add a second GPU and I would like to make sure it does support the extra voltage. P.s: I already installed a secondary GPU when I had the access and I rushed outside the server room. When I later checked, the second GPU was not recognized (now that I don't have the access anymore!! :P) I wanted to make sure if the problem was the lack of power voltage as the GPU was working on another machine and is not faulty. Currently, I don't have physical access to the PC currently (ssh only). I have tried to see other posts, also the other exisiting tools, i.e., sudo dmidecode -t 39, sensors, and ipmitool, but none of them show the information I'm looking for.
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I'm trying to wire up 6 RGB LEDs in parallel, all controlled from a single source (well, three sources, one for each colour). The LEDs came supplied with resistors to limit the current of 270 Ohm for a 5v supply.  The problem is, 6 LEDs x 3 colours = 18 resistors, which is a lot, and means I need a much bigger board and a lot more soldering.  So, can I instead wire the LEDs in parallel with each other, with a single resistor protecting all six? (3 resistors in total, one for each colour). How do I calculate the value of that resistor?  More details:  The LEDs are being driven from a  to supply a bit of current, which is in turn controlled by a Netduino providing a PWM signal on the three channels.  . If I've correctly understood the data sheet they want 20mA of current, and forward voltages of 2, 3, 3 volts (for R,G and B respectively?). The supplied resistors were all 270 Ohm, so the channels may not be balanced quite right.  For extra credit: I'm only using 3 of the transistors in my driver chip, which has 8 in total. could I wire the PWM from the netduino to a second trio of transistors, and split the LEDs into two groups of three? Is it worth the effort?  PS I don't have any diagramming tools to hand, but I can provide a diagram (drawn in paint) if it would help clarify my question. (see also )
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I just designed this MPPT solar charge controller which outputs 4.2 V regulated via MPPT, it uses the SPV1040 IC. This will be used on a satellite with 4 side panels, each with 8 solar cells in parallel outputting 2.6 V at approximately 122 Ma. Each panel will have this exact circuit and all the outputs will be connected in parallel to a 3.7 V lithium ion camera battery.  When active only 1 solar panel will be active and the other MPPT circuits will be offline or providing a very low amount of current. How should I connect the 4.2v to the battery, just directly or using some sort of controller to stop charging at 4.2v? Keep in mind the battery will always have a load and it will charge for around 50m in a 90m cycle due to being eclipsed. I would obviously like the battery to last as long as possible so I am not sure what are the implications of constantly having a battery connected to 4.2 V during 50m. Thanks.   The schematic was made based off a simulation made using the ST Edesignsuite directly from the provider.  Excuse my previous question about this, wasn't properly worded.
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I am using a 36 V battey pack (10s 2.5 A each cell 3.6V.) Its maximum voltage is 42 V. I am using a STM32 microcontroller whose input is 3.3 V.  I am designing a PCB in which the power supply is drawn from the battery pack (42 V.) I would like to power the STM32 microcontroller from the battery pack power supply.  I would like to regulate 42 to 3.3 V so that I can power my STM32 microcontroller.   Which method is best to convert it either using regulator or buck converter based on the pcb designing?  Battery Specification: 10s1p   Battery pack nominal voltage: 36 V Battery pack maximum voltage: 42 V Battery pack current: 2500 mAh   Microcontroller specfication: STM32F401RCT6   Supply voltage: 3.3 to 3.6 V Supply current: 100 to 160 mA     Which method or component is best to regulate 42 V so that I can power my microcontroller with 3.3 V?
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I am trying to make an electric go-kart. I am new to the forum, so I may be missing some information but any help is greatly appreciated. After doing some math and discussing with friends I found the following with the given information. I have 4, 24V 14A motors, all connected to a read drive axle. I have 2 pairs of motors on each side of the drive axle. The motors have an 11 tooth sprocket that is chained to a 68 tooth sprocket that is connected to the drive axle. I currently have 2, 12V 7Amp 20 hour lead-acid batteries, which provide my 24V. Each pair of motors is connected in parallel to ensure they both get the 24V. However, the motors do not spin, even when there is no load (The wheels aren't contacting the ground). I believe that this may be because the motors do not have enough amps, only receiving 7 Amps of the 14 Amps from the batteries, because there are 2 motors in each pair. My main goal is to get the kart moving. I weigh about 130lbs, and the kart is likely around 30lbs. Would getting a battery/batteries with move amps (28A) allow the motors to run properly? Any advice is really appreciated. All the information I know Each motor is a DC motor that needs 14A and 24V The motor has a sprocket of 11 teeth The Watts of each motor is 250 The motors are rated to have an RPM of 2750 or around 45.83Hz The drive axle has a sprocket of 68 teeth. The 68 toothe sprocket is 5.5&quot; The wheel diameter is 10&quot; If my math is correct, given the ratio of the motors to drive shaft. Each motor produces 5.45Nm of torque, and after the sprockets, the torque is 33.69Nm. I don't know what impact the 4 motors would have on the torque, nor do I know what the torque is for each side. I really just want this kart to move. Would removing motors allow my vehicle to move? I think that my power supply does not provide enough amperage to my motors. Would having 1 or 2 motors be better in this situation?
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I have read that using a higher voltage motor would need less current to get the same power. I understand that P = IV and how that works. My question is if the 24 V motor would get half of the current, wouldn't it have half of the torque as well since they are directly proportional? In that case I don't understand how the 24 V would be advantageous at all.   Typically when people talk about motors a higher wattage motor is "better". I don't understand physically how more watts makes the motor "better". It just means it uses more energy per second which I guess would mean it is all converted into mechanical energy but not torque? I don't understand the relationship there.
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I want to control a siren speaker (has a built-in driver) with an Arduino.  The siren needs 12V and consumes about 480mA. The Arduino output pin is 5V and can source 40mA maximum.  I would like to use a transistor to switch the siren on and off. Is this an OK application for a transistor? I'd rather not have to use a relay or a SSR because I don't have any on hand.  Based off of those numbers I calculated my load (siren) resistance to be 25 ohms using Ohms law, R=E/I. (I'm using Amps, Volts, and Ohms as units)  $$\frac{12V}{0.48A} = 25 \Omega$$  I have found various calculations to determine what kind of transistor I need and I'm not quite sure which is the best one. One of them is like this:  $$h_{FE(minimum)} = 5 \times \frac{Load\;Current}{Arduino\;Pin\;Max\;Current}$$  Which gives me a minimum \$h_{FE}\$ of 60.  $$5 \times \frac{0.48}{0.04} = 60$$  This is where I get a little confused. I have a few transistors and their datasheets but I'm not quite sure how to read them. I have read many resources and I am just as confused now as before.  I know I should probably use a NPN transistor but would it matter if I use a PNP instead? Do the same calculations apply? I understand that the circuit changes, active high instead of active low, but are there any drawbacks to PNP over NPN?  The NPN's I have are , ,  and a .   The PNP's I have are ,  and a .  How would I go about choosing the right transistor for the job? I don't want to overload the transistor.
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I am trying to build a DC-DC Buck-Boost Converter using  basic schematic and an Arduino with the analogWrite() function as my PWM generator. I only want to step up 2.4-3V to ~5V. If it's just the capacitor and no load, the converter works so good that I have to switch it off after a few seconds since the voltage I measure on my capacitor is exceeding the capacitor limit. However, when I connect any load to the capacitor(for example a motor or a resistor) my voltage drops to a really low value(0.1-2v) and stays that way no matter what frequency PWM signal I send to the transistor using Arduino. I really tried but couldn't find the cause of the problem. Is it because I have two grounds, the battery pack one and the Arduino one? Is it because of the inductor(I tried using a smaller, 45uH, torroidal one but couldn't get any better results)? So what am I doing wrong?   I only expect to draw 500mA of current at 5 volts at the output side, and according to  calculator my inductor and transistor should be fine.  Components: 100uF 35V electrolytic capacitor, 200uH inductor, BYW29 rectifier diode, TIP 120 power transistor, 1k resistor    A schematic of the circuit or at least how it is supposed to look. Maybe I miswired something? The resistor is to represent  the load, the value doesn't matter since my problem persists at any value but the multimeters "infinite" resistance.   This is how my circuit looks   I used one coil of an old transformer as my inductor    However I also tried this inductor
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One concept of electronics I have a hard time understanding is if things like motors, actuators, solenoids etc. use as much power as they need or what you give them.   If a motor needs 12 volts and 500ma and I supply it with 12 volts and 3000ma will it only consume 500ma? Also, if I supply it with 15volts and 500ma what will happen?   It seems logical that an LED and a DC motor are way different when it comes to requiring/using electric where as an led has to be completely regulated and (I assume) a DC motor doesn't.   Is my understanding wrong?
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I've been working on a data logging device that will eventually go into my personal vehicle.  I've scoured the interwebs and built what, in theory, should be a fairly stout power supply capable to handle fast transients and undervoltage and the fabled load dump.  My problem is, though... I want to actually test the power supply.  In previous questions that I've asked related to the design of the power supply portion, I've been told that the "right way" to simulate a load dump is with a proper, preofessional testing device.  I'm curious, though... what's stopping me from rigging up something that is "close enough"?  My idea is simply this: get a low-voltage DC power source, such as an old PC power supply.  Get a DC-DC converter to step that 12V up to something in the 80V range.  Assemble a bank of capacitors to get me in the neighborhood of a theoretical 12V load dump..  which from what I can tell is in the hundreds of joules range.  Once charged, simply connect it to the battery input of the device - which wouldn't be connected to an actual power source lest I want to potentially screw that power source up - and see if explodes, and if not, see if it works normally afterwards.  Does this sound like the dumbest idea you've ever heard?  Is it a somewhat decent idea that simply needs a lot of planning and number checking to in order to work roughly as intended?
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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:
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So I'm trying to power 2 of these  together in series. I know that I have to add the voltage of the two lights together and get a resistor that restricts the power to that level. I have a 9V battery and the lights are 3V each. I brand new to all of this, and understand almost nothing, so any help would be appreciated. Can someone help me choose the correct resistor (And how to identify that resistor with the color branding thing) so two of those lights listed above can be wired in series? Thanks!
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I have a 6V 3AMP power supply and I wanted to reduce the voltage output to 5V 3AMP.  I saw buck converted on ebay of the following spec. Can i use it to step down 6V to 5V without losing Ampere? or any suggestion, how i can step down 6V to 5V while keeping 3AMP.    DC-DC Buck Step Down Converter Regulator Power Supply Module 9V 12V 24V to 5V 3A.  Mini DC-DC Step Down Converter  Input voltage 7V~28V  Output voltage 5V(Precision 1%）  Output current 3A(max),long time work within 1.5A  Conversion efficiency 96%(max)  Output ripple &lt;30mV  Switching frequency 1.5MHz(max), Typical 1MHz
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Imagine I have a 10V battery with a capacity of 1Ahrs connected to a 100 Ohm resistor.  I'll get 0.1A (V/R) at a power of 1W (current x voltage) for a total of 10hrs. As a watt is defined as J/s my battery produces 3,600J (1x60x60) in total.  Now, imagine I get a second, identical battery and connect it in series to the first one. I will effectively have a battery of 20V with a capacity of 2Ahrs, all connected to the same 100 Ohm resistor.  I'll get 0.2A at a power of 4W (current x voltage) for a total of 10hrs. This will generate 14,400J (4x60x60).  So, from doubling my energy source I have quadrupled the energy output!  I've obviously made an error somewhere either in my calculations or conceptual understanding, and I would be most grateful to anyone who could set me right.  Thanks!
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I have this working         &ndash; Schematic created using   An Arduino commute both relays and a power adapter charge each battery at a time.  I would like to replace each relay by a MOSFET. How can I do that?  I think the solution bellow will not work because DRAIN is always connected to SOURCE and this will short circuit batteries. MOSFETS only isolate from SOURCE to DRAIN.  When the D9 is HIGH, D10 will be LOW so the power adapter will never be charging both batteries simultaneously.          Sorry for the messy schematic.  Thank you very much.
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Is there anyway I can connect resistors to allow them to take more power such as using 4 1/4 watt resistors to get a 1 watt resistors. Or do i just have to use 1 1 Watt resistor.