# Tag Info

1 vote
Accepted

### Determine the min/max resistance of an SMD variable resistor

Since it is a 15k potentiometer, ideally it will have exactly 15k resistance between ends, and when the wiper is at one end, there will b 0 ohms between wiper and end, and of course 15k from wiper to ...
• 89.2k

### Average voltage in PWM?

If you have a simple first order RC filter which removes PWM switching frequency but leaves the DC voltage, it has the correct output voltage, but due to the resistor, the output impedance at DC is ...
• 89.2k

### Average voltage in PWM?

In every DC-DC (buck) converter you will find an inductor that is connected in series to your PWM output and a parallel capacitor that is connected to the inductor output and ground. Together, these ...
• 13

### DC/DC Converter not outputting the correct voltage

It's simply the wrong part… the LT3463A is a boost converter so if you feed it 3.5V you can't get a regulated lower voltage on the output. The topology is easily recognizable since the inductor is on ...
• 7,658
Accepted

### DC/DC Converter not outputting the correct voltage

Simple enough, the positive regulator is a boost converter and output cannot ever be below input voltage -once granted voltage drop on D1-
• 2,977

### How should I use this voltage regulator for best efficiency?

If you don't need an exact regulated supply, you can put a schottky diode between battery and the common board supply. If the MCU is aware of the battery voltage, it can bypass the diode with a P ...
• 1,889
1 vote

### Is there a good way to insulate the backplate of a 7915 voltage regulator?

Mounting TO-220 and similar packages to a heat sink while maintaining electrical isolation is common. One example is that it allows one large heatsink to host a number of devices, each with a ...
• 599
Accepted

### Is there a good way to insulate the backplate of a 7915 voltage regulator?

Here's how. The insulator between the device and the heat sink is a mica shim and that between the device and the screw is an insulating bushing. Image credit: Infineon.com
• 10.4k
1 vote

### How should I use this voltage regulator for best efficiency?

Assuming linear regulator. What features of the voltage regulator should I pay attention to for lower power consumption? Quiescent current, obviously, including feedback resistors. That pretty much ...
• 59k

### Voltage and current controller problem

You cannot control the voltage and current in a resistor independently. That is why your circuit does not work as you intend it to. I presume you have heard of Ohm's Law. If you apply it to your load, ...
• 58.5k
1 vote

### Using Jfet as constant current source to drive a BJT

I suspect that the first circuit is intended to provide a constant current limit for low load resistances. Once the voltage on the load drops below Vref, the op amp is effectively disconnected. Then ...
• 58.5k
1 vote
Accepted

### Using Jfet as constant current source to drive a BJT

When using a JFET as a 1 mA constant current source, the maximum current that can be drawn into the TIP41 base is 1 mA and, given that the hFE of the transistor is only going to be around 50, the ...
• 384k
1 vote

### Using Jfet as constant current source to drive a BJT

I agree with @TimWilliams that these circuits are a bit strange. But in general low noise current sources can be made with JFETs, see here. However, in these circuits, this advantage would not ...
• 10.8k

### What capacitor do I need for an AMS1117-3.3 regulator?

The datasheet you linked specifies a single 22uF tantalum cap on the output (see Application Hints - Stability). Bulk capacitance on the input is up to you if you want it.

### How to power two ESP-01S chips from 220 V AC

Be aware to know the complete specifications of the supply of ESP-01. from this link. And for the need of only supplying ESP-01S, I choose some SMPS converters (google it "AC 220V 230V to DC 3....
• 4,742
1 vote

### How to power two ESP-01S chips from 220 V AC

You can use a "wall wart" USB power supply with an LDO or buck regulator, or a power supply module, like this MeanWell RS-15-3.3 : It is preferable to source it through an authorized ...
• 331k

### How to power two ESP-01S chips from 220 V AC

The 2 most important rules of small/hobby electronics: Don't mess with AC mains power. It will kill you. * Don't reinvent the wheel. It will frustrate you and waste your time. src ** Now you only ...
1 vote

### Transistor voltage regulator circuit - question about voltage output control

The circuit is best understood by redrawing it to make it easier to understand. Q2 is is a simple Emitter Follower buffering the voltage on the Zener. You don't mention the Zener voltages so below I'...
• 21k

### Need help identifying SMD IC

Function and pinout matches TPS560430Y, but there may be others with this pinout. The inductor 2.2 µH is a bit small for this circuit, but OK if used with <= 12 V input.
• 1,889
Accepted

### Capacitor selection with current rating for switching regulator

The info is a bit hard to find. For Murata, you can use their website (click on ceramic capacitors). Then, picking a capacitor, you can plot "Temp rise" (orange button) which will tell you ...
• 59k
1 vote

### How does a switching regulator behave if its input is equal to its output?

Depends on type. LM2596 for example, I believe can run up to 100% duty cycle, but has a Sziklai type output stage, so drops about a diode drop minimum, or about 5.8V minimum input (unless the control ...
• 2,413
Accepted

### How does a switching regulator behave if its input is equal to its output?

It depends on the specific regulator. Some buck regulators have 100% duty cycle mode. In that case, the top FET turns on, and it's just like having a resistor between Vin and Vout with a value equal ...
• 19.7k

### How does a switching regulator behave if its input is equal to its output?

Most DCDCs configured in buck mode will try to operate at 100 % duty cycle -- i.e. the high-side switch will be 100 % on. In the LM2596, since the output is a BJT device, this means that the output ...
• 13.9k
1 vote

### Can a voltage stabilizer with an offline UPS give the same performance as an online-UPS?

It works fine during a complete loss of grid power, but when the grid power flickers the cluster shuts down. The instant you lose grid power, treat it as a complete loss and drop a relay that ...
• 384k

### What happens if input current of 2A is given to a L7805 rated of 1.5A?

Not knowing which brand or version of the 7805 you have, there's no way to know the specifics of how it will act. Many 7805 have internal current limiters. And thermal shutdown. One brand's datasheet ...
• 71k

### What happens if input current of 2A is given to a L7805 rated of 1.5A?

The provided input does not matter. What matters is how much current the load consumes at 5V. The regulator can accept 12V input, and it can provide 5V at up to 1.5A. But it can't do all that ...
• 89.2k
1 vote

### What happens if input current of 2A is given to a L7805 rated of 1.5A?

Regulating 12V to 5V with a linear regulator is a very inefficient method to do the job. With 7 volts dropped across the regulator more power goes into producing heat than actually is delivered to the ...
• 55.3k
Accepted

### Using a 5V voltage regulator with a 5V input

the professor stated that, even if the input will be the same as the output, one should normally use a voltage regulator regardless. Nope. A linear voltage regulator can't produce an output voltage ...
• 59k

### Using a 5V voltage regulator with a 5V input

You can't get 5V outof a linear regulator supplied with 5V. There is always a voltage difference between input and output for a linear regulator. The AMS1117 you specify in your schematic requires a ...
• 58.2k
1 vote

### Designing A Circuit To Light An LED When Voltage Drops Below Threshold

Why are these two equations different? As far as I can tell the Sparkfun material is simply wrong. But it's hard to understand. For example, they say what will happen when $V_{in}$ is greater or ...
• 121k

### 14-Volt 6-Amp Power Supply Stability

OK, it would be better with a switcher, everyone said it. With 20V input, 10V output, 6A, the MOSFET will dissipate 60W. If there is a 6A current limit and the output is shorted, it will dissipate ...
• 59k
1 vote

### 14-Volt 6-Amp Power Supply Stability

simulate this circuit – Schematic created using CircuitLab I think there are too many problems with your present config. options: Battery charger design 14.2V + motorcycle battery, stable, most ...
1 vote
Accepted

### Can I power my microcontroller system directly from a 3V lithium coincell (transient consideration)?

The nominal voltage is perfectly in spec, as pointed out by Autistic. On the other hand, ESD and hotplugging events are two different things. An ESD event can expose the circuit to thousands of volts, ...
• 2,394
1 vote

### Connecting two voltage regulators in series to get higher voltage

If the panels match coarsely on current rating but not voltage, wire them in series. They will work at the spec of the smaller panel, which is no big deal if the difference is small. If the panels ...
1 vote

### Can I power my microcontroller system directly from a 3V lithium coincell (transient consideration)?

It will be fine ,Volts are not too high when the coincell is fresh.Normally there are lots of bypass caps that would suck up any little spikes.
• 12.4k

### Connecting two voltage regulators in series to get higher voltage

I wouldn't advise it. If one of the solar panels is covered and doesn't produces power, you might have current externally "forced" through the second converter (which might suffer from it). ...
• 2,646
1 vote

### Connecting two voltage regulators in series to get higher voltage

This is possible if you use isolated DC/DC converters. If you use a LDO or something similar, the negative output is typically assumed to be at the same voltage as the negative input (and the two ...
• 756
1 vote

### Can you connect two LM317s either in series or parallel to help spread out heat?

Instead of another LM317, one could also use a MOSFET or NPN in series as well. This can even be done with a zener to make sure only a small voltage will be across the input/output of the LM317. A ...
• 59

### Voltage divider, linear regulator, other options to power proportional HV DC-DC converter?

As said by Andy aka, using a version with a control pin is the easiest way to accomplish your goal. However if you already have the EMCO converter and can't buy a new one (they are fairly expensive) ...
• 105
Accepted

### Voltage divider, linear regulator, other options to power proportional HV DC-DC converter?

You should consider using this converter inside of a closed-loop controller. The output voltage could be precision divided down to produce (say) 1 volt out per kV in and you use an op-amp controller ...
• 384k

### How do you regulate a car battery down to exactly / not more than 12V?

Typical 12V led strips have resistors that only provide about 17 mA at 12V. They are sized for auto applications like a cars "12V" system already. At 14V of a typical alternator powered 12V ...
• 71k
Accepted

### How do you regulate a car battery down to exactly / not more than 12V?

I have 2 different solutions : 1 ) Why not use a linear regulator with low drop voltage (sometimes they are classified ad LDO (Low DropOut), sometimes you have to sort/filter by dropout voltage). You ...
• 2,646

### Switching regulator voltage issue after rework

If your switching regulator is acting strangely, check to see whether it is oscillating at high frequency. I've had experience of a TI part that had a great tendency to oscillate around 250 MHz; ...
• 679

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