# Tag Info

1

A traditional power supply based on a line-frequency transformer is reasonablly easy and safe to build, since the only things on the main side are the line side of the transformer and any protective devices. All the electronics are safely on the isolated side of the transformer. However at typical electronics power levels, line-frequency transformers are ...

1

i have been working on power supply from transformer and to flyback SMPS, and some PS i create is definitely overpriced / overcost even the basic power supply with common transformer. it didn't even worth it to create "The best most stable PSU", it just not worth enough your time and cost but probbably just enough for experience, if you are not even have a ...

0

I'm going to ignore the risk of electrocution or shock, since 110V is weaksauce anyway and you'd have to be super unlucky to actually hurt yourself with it. That said, the major downside for me is that the cost of components to build your own power supply is much higher than just using a mass-produced wall-wart or phone charger. Additionally, unless you'...

2

To try to expand on a few answers a little... Firstly, if you're talking about a low-voltage PSU (ie. something that takes 12V or 24V in and pushes out 12, 5, 3.3 etc - then I'd say it is worth doing yourself, although you may find breakout boards that do a lot of what you want are available pretty cheaply. These days, little buck converters seem to be ...

2

Here's how that works in the real world. Option 1: Use a Wall-Wart that is already UL-listed. You design the DC side of the product, and pack it off to UnderWriter's Laboratories to be tested, along with some of the wall-warts. UL sees the wall-warts are already UL listed, and makes no further investigation. They focus on the low voltage behavior of ...

0

sticker on the adapter says the range is 100-120v If the adapter is said to be complaint with 100 - 120 V, without any design knowledge, it is best left to use for the ONLY intended voltage range. It might work, but it might not fulfill all the necessary safety requirements at a voltage rating higher ( or lower) than the one specified, this may put you ...

2

Sure you could buy a supply or but if you want to learn and time for your hobby is not a problem then take a shot at a power supply. Manufactures spec sheets have a ton of info and often reference designs. A stop-gap or workbench solution if you need more power is take an old PC supply and hot-wire the startup, remembering that some require a load before ...

4

35 or more years ago, almost every kit radio and electronic hobby project required building some sort of linear power supply. Diode bridge, or even vacuum tube half wave. Most Apple 1’s, for instance, have two big transformers. A whole bunch of us old computer hobbyists, engineers, and scientists are still alive. One doesn’t learn nearly as much ...

8

Even for mass-market consumer devices it's often worth it to not design a custom power supply, or even integrate an off-the-shelf power supply into the device. Going with an external power supply saves you from having to design & certify the device to avoid shock hazards, and once you do that you might as well use a commercial off-the-shelf external ...

2

As far as I know a transformer, bridge rectifier and a circuit with several LM2596 or other switching power supply IC to generate 3.3V, 5V and 12V doesn't seem hard to make, but are there any downside other than risks of shock ? Linear power supplies are quite simple to make, and the risk of shock is low if you properly insulate the mains side and keep ...

14

If you're building a few for personal use, I'd say it's not worth it unless part of your goal is to learn power supply design techniques and principles. Even then, it's much safer to get a wall wart to convert your line to, say, 12VAC for safety. If you're planning to go into production with it, you should consider your volumes first. The lion's share of ...

5

To design and implement an off-line power supply is indeed dangerous, since the 110/220 V at the mains and the rectified DC voltage can be lethal. Other than risk of shock, one need to take care of clearances and protections. I would recommend to someone without experience in the subject to buy a power supply, like your Meanwell power supply. A cheap PC/...

0

The first approach was to use a mosfet "ideal diode" in series with the power supply and a big capacitor across the input. However I failed to find a capacitor big enough that is also rated for automotive use (at least 16-18V). Have you checked the automotive audio section of a local store? You can usually find a 2-5 Farad 16-20V capacitors that are ...

0

simulate this circuit – Schematic created using CircuitLab Figure 1. The connection scheme - five single-phase loads on a three-phase supply. What you are proposing is normal practice. Most single-phase circuits are just one of a three-phase supply with return on the neutral. Ideally we try to balance the loads on all three phases but there is no ...

0

I would like to find out which pin carries the battery voltage, and which one is the ground. The three other pins are much lower voltage, sending 52V to them would cause damage. Modern digital multimeters typically have an input impedance of 10 MΩ. They are so sensitive that they can for many practical applications - such as your battery measurement - ...

1

Yes it most likely work. It doesn't make much difference in linear power supplies because you don't have much of ripple at the input. tantalum capacitors usually used for switching power supplies, where ESR matters. The resistor on the emitter is to match the transistors. it's called fixed bias which you can read more about in here. and for this design you ...

1

The most important property of an inductor used in an inverter circuit is the current allowed to run through it. A tiny axial inductor may have the same inductance as a radial one but most likely it has a much smaller maximum current. The inductance needed depends on the voltage spread you want to achieve. I recommend to stick to the datasheet of the ...

0

Inductors have several important specifications. It does not matter what the construction is, axial lead, pot, whatever, as long as it meets your specifications. Generally the larger and more expensive component will tend to have better specifications. Once you've met your converter specifications, for power throughput or efficiency, there's no need to go ...

0

The connections on your bridge rectifier are completely backwards. You have AC from the transformer connected to the rectifier's + and - outputs and you have the DC outputs connected to the rectifier's AC inputs. All the grounds in the circuit should be connected together.

0

Maybe buying a 24v AC - DC Power supply, and with a resistor ladder divide in half the voltage at the input, hence creating a virtual ground at 12V. But this 12 V will be the ground supply for your circuit. For voltage stability you can put a 7812 to regulate +12v with respect to virtual ground, and a 7912 to regulate -12v with respect to virtual ground.

1

The simplest workaround to an un-activated BMS (sleep mode) is to supply it with power from it's own batteries. To achieve this, a push switch/momentary switch can be used between the P- and B- terminals of the BMS. Note: This will work only if the cells have adequate voltage. The BMS will return to sleep mode if the individual voltages are too high or too ...

0

The LED light you have is a Blackbox. We do not know the configuration of the LEDs (if there are multiple). The power supply internal can be a buck regulator, or even a buck boost regulator. The LED driver IC type is also unknown. It can be probably a flash LED driver (example: STCF05) Operating a device with minimum voltage with boost regulator will ...

0

What you are experiencing a loss of power during switchover between power sources. In your case you have 2 DC power sources and 1 DC power consumer and the power consumer(your gaming rig) accepts a wider input voltage. The simplest solution could be make grounds of your rig, and both power supplies common. On the positive(+) output of each your power sources ...

2

Since we don't really know how much power the router needs on average, it is hard to size the panels. The 2A rating is most likely the maximum that is required, not the average. So my suggestion is to use two of the 20W panels in parallel. You will also need some type of voltage regulator to protect the router from over-voltage. Please note that the router ...

1

You are detecting Peak current and not Average Current as should be !! Where are your specs???? A BLDC fan acts like a resistive load ONLY when you average the current over a specific time interval such that there is no ripple in the Avg current measurement. As such, the fan current increases linearly with voltage above the start speed due to RPM fan load....

4

I suspect leaving 0V outputs floating will result in unstable operation or oscillation. The datasheet seems to imply that minimum load for regulation is 10% of max current. Therefore I'd suggest adding small loads to the outputs. For example 1.5k for 10mA current.

0

So it looks like a typical 1W LED will drop about 3.3 volts. This same LED will draw around 0.3 amps according to various references. The resistor you are looking for will need to drop the other 8.7 volts (12-3.3). (V/I = R) 8.7 volts / 0.3 amps = 29 ohms. So power dissipation for this resistor will be P = VI 8.7*.3 = 2.61 watts. Much bigger than the ...

0

It depends on whether your 15v power supplies are isolated. Some are, most aren't. If it's not isolated, then the -15v outputs of the PSUs are both at -15V in reference to the input ground, not just 30V below their own respective high rail.

6

Per the datasheet these supplies have isolated outputs, so you can offset them from the input. All you need to do is avoid creating ground loops, and let the (nominal) 0V outputs float to the midpoint of the 30V rails each one produces.

1

Sorry, but brushless motor is a complex load. It has electronic commutator which switches the input voltage to the winding or windings which currently are best to keep the motor running. The load is not pure inductance, there are controlled switches in series and the controller itself. If your current limiter causes voltage drops they can disturb the ...

0

Yes, an induction machine always consumes reactive power, both working as generator or as motor (more common case). Reactive power is necessary for the operation of any induction machine. Source: https://en.wikipedia.org/wiki/Induction_generator

16

It doesn't entirely excuse the poor performance of the MCP1700, but I think you'll generally find that very low Iq regulators tend to have much poorer high-frequency PSRR. You would not expect an op-amp with a very low quiescent supply current (a couple uA or less) to be very useful at high frequencies, and the error amplifier in the regulator is no ...

6

This is cheery picking functionality of a particular part. An ideal LDO has infinite PSRR so what is the limiting factor on real LDOs that degrades performance at high frequencies? I recommend you read this article to really understand noise in LDOs. Read this article to understand PSRR and don't confuse the two. The two are often confused and often people ...

11

My practice is to use a large enough capacitor before the LDO to handle high frequency ripple, with a small R or L before it if necessary, and rely on the LDO to remove the low frequency variations. That means both components get used at their 'best' frequencies, and I'm not requiring either to struggle to work where they are not so well specified. If the ...

-1

A quick skim of the linear regulator section of my Nat Semi data book turned up several ICs with 40 to 60 dB rejection above 100 KHz, so 'Dave' was cherry picking as you suspected. Just another reason to not watch videos; do real work on real circuits instead.

19

In the case of the MCP1700, Dave is certainly correct. Here's the ripple rejection versus frequency chart from the datasheet: The datasheet itself claims 44dB of ripple rejection at 100Hz, which agrees with the chart. It also clearly shows how poorly it handles high frequency noise. The LM317, on the other hand, gives you better than 50dB of ripple ...

0

The datasheet of the LM337 shows what the parts should be (the schematic is correct) and how to calculate the setting of the potentiometer and the input voltage to get an output voltage. The 15VAC input has a peak voltage of 15V x 1.414= -21.2V and the rectifiers reduce it to about -20V. The 120 ohm resistor and 2k pot can be calculated for the LM337 to ...

0

Never heard about "burst-mode". Pulse skipping is a simple method to limit the output voltage / current within the maximum permitted margins. The simplest analogy is a children swing. You push every cycle in resonance as long you have enough amplitude, then you skip pushing until the swing goes lower. In a resonance circuit there is a similar behaviour, if ...

0

root of mean of squared current, thus: $$RMS= \sqrt{ 0.38 I_x^2 + 0.62 I_y^2 }$$

1

You can use the 18v, 20 watt solar panel to power your router. Just make sure it doesn’t go cloudy or your internet will cut out. I recommend a battery backup. You cannot directly connect your 18v to your 12v input either. You need an adaptor in between. I am assuming dc. Look for a 12v dc-dc convertor like this one: https://www.amazon.com/Ultra-MP1584EN-...

0

There are some couple of solution to bring down the power dissipation Transformer secondary voltage can be bring down to somewhere near 15V Use Switching regulator instead of LDO's

1

As others have said - a lower voltage input to the regulators will decrease power losses. Ideally Vin is about Vout + Vdropout + Vheadroom Where "Vheadroom" is a volt or two. Where you have excessive Vin, dissipation in the regulator can be moved into a series resistor that can be dimensioned to withstand the dissipation. If 5V is used, connecting the 5V ...

1

What you have. What you need to make it work. A 20A Pch FET.

1

Yes, the 7812 is overheating and should be shutting down. The +28V input is way too high and creating too much heat. A 24V center-tapped transformer will produce a rectified and filtered 16v which will be fine if your electricity does not have brownouts. The datasheet for the 7812 shows its thermal resistance and finned aluminum heatsink manufacturers show ...

1

Not with a 3-wire fan with a tachometer (TACH) output like the delta fan, the FG signal is for speed monitoring and it outputs a signal. Source: https://www.delta-fan.com/Download/Spec/AFB1212GHE-CF00.pdf One way would be to change the voltage which could be done with a variable resistor in series, but one problem with this is approach is the remaining ...

1

The motherboard is able to control 4-wire fans using PWM, and 3-wire fans using DC voltage level. I did not see anything about 3-wire fan support on that page, but if user manual says so then you don't need anything else but correct wiring on 3-pin plug. The PWM control pin will not be used, and the taho output from 3-pin fan is compatible with tach input ...

1

I'll try to explain simply... WS2812B draws pulsed currents from the supply. When you have lots of these LEDs, the high amount of varying current will create voltage drop across the supply wires, which have both resistance and inductance. This causes the supply voltage to ripple, which will crash your microcontroller, and also makes the controllers inside ...

2

Try adding decoupling capacitors. Decoupling capacitors are like sugar and your primary power supply is like fat. The first is fast and on-demand, the second is high energy but slow. If you try to do strenuous activity and your blood sugar is low, you pass out. Same thing with circuits, more or less. All connections have inductance so sudden changes in ...

0

Your power supply will still work. However doing so means that you no longer have isolation between the primary (input) and secondary (output) sides of the power supply. Whether or not this is a problem or a violation of some requirement depends on the particulars of your system. Many systems require that the primary and secondary returns (grounds) of ...

0

When you short the output ground to input ground, there is no isolation anymore. However, the outputs still give you the specified voltages referred to input ground.

Top 50 recent answers are included