# Tag Info

2

The key things to figure out are: Regulator current Voltage drop The first you've stated as 700mA. The second we'll figure out. 24V AC will regulate to 24V/0.707 = 34V DC. With 24V output, we have a drop of as much as 10V (34V in - 24V out.) 10V at 700mA will dissipate... 7W in your part, worst-case. That's kind of a lot for the LM317 / 337 in TO-220.

1

In a typical DC/DC converter a proportion of the output voltage is fed back through a voltage divider into the regulator IC, which compares it to an internal reference voltage and raises or lowers the output voltage to make the feedback and reference voltages equal. The block diagram looks something like this:- simulate this circuit – Schematic ...

0

Presumably the 555's threshold pin is connected to the inverting input of the op amp. Swap the inputs over on the op amp. 555's threshold pin to the op amp's non-inverting input and the pot to the op amp's inverting input. And do put a current limiting resistor in series with the LED.

1

Here's the simplest thing I could come up with quickly off the top of my head. It uses the requested 3 active components, but there's a bunch of passives including the not shown decoupling caps. When the input voltage is below the setpoint (set by voltage reference/zener D2) the comparator output is low, and the PFET is on, shorting out the dropping ...

1

The current drawn depends on the LOAD (whatever the LM7805 is driving). It's gonna output 5V regardless the input voltage. What changes is the POWER DROPPED in the regulator. Instead of dropping 15V->5V, it has to drop 20V->5V Which means the POWER consumed IN THE REGULATOR will increase about 50% (Load power is unchanged) This all comes from ...

0

What I know at the moment is that Voutput=R3A+R3BR3BVD, but I don't know what determines the extremums of the output. The dominant factor will be the "reference" diode. You need to be aware that forward-based diodes aren't all that good at setting a constant voltage for varying currents. As a rough starting point, figure that the forward voltage of ...

0

Unclear what you mean by "extrema" so I'll answer this: I also hope to know what these differences affects the regulator briefly. the direction the diode Usually a zener diode would be used as reference, so it would be in the other direction. If you use a standard diode you'll get a 0.6V voltage reference. Since R3A=R3B you'd get 1.2V output. ...

0

Your method clamps the input signal to Vdd (3V3) + a diode drop (0.7V) or GND - a diode drop. This makes a lot of sense. I/O signals that exceed those limits will be limited and not cause any damage to following circuitry. One thing to be aware of is that it's important for the input signals to swing close to GND to ensure that correct logic levels are ...

5

Overview Re-drawn in more readable format: simulate this circuit – Schematic created using CircuitLab The whole thing now basically makes sense to me. The way you drew it is more like what I see in a magazine, somewhere. Also, I notice that you are using an MJE13007. Did you source that power BJT from a failed compact CFL? It's the kind of BJT that ...

10

Your output transistor is a high-voltage part and has exceptionally low hFE, as low as 5 at 5A. If the hFE is actually, say, 10, at 5A out, the poor BC547 is being called upon to deliver 0.5A with around 13V across it. That's 7.5W in a TO-92. Reminds me of a problem I had recently (actually it was metalworking rather than electronics, but the principle is ...

2

The first capacitor --- 10,000 uF --- is too small. That only supports 1 amp drain at 1 volt ripple at 120 Hertz.

2

What happens if I use this Inductor in both input and output path? The inductor you linked is 0.47 uH so, it will be ineffective as a filter but have no problems with the operating current. I am unable to find the part number for matching the recommended value(10uH to 47uH) in 0805 package at the input and output current rates of 2A. Yes, that doesn't ...

2

The maximum load current is when then zener no longer has sufficient current to regulate. Since we don't have any information about the Zener diode itself, we can assume it to be perfect so it stops regulating when the zener current drops to zero. That's actually a reasonable assumption for an 8V zener. The worst-case conditions on the low side are minimum ...

0

Here is a block diagram of the LM2596HV from this datasheet: If the switch transistors fail shorted or the adjustment pot is turned too far to the wrong direction the output voltage can be as much as the input voltage (minus a very small drop from L1). The Absolute Maximum input voltage for the Raspberry Pi 3 (and 4) is 6.0V. The LiPo cells have a maximum ...

0

This is the simplest and easiest switching converter to understand: - The input voltage is modulated by the switch's duty cycle to produce an average value that corresponds with the required output voltage. The LC acts as a low pass filter and converts the modulated duty cycle from above into a steady DC value. There are mathematics involved if you want ...

2

This seemed to be a problem with the value of the capacitor I was using after the LDO. Below are some screenshots: This is the LDO, using a ~4uF capacitor. Note the dips 300mV (which is HUUUGE) And this is the LDO with the right 100nF, as pointed in the datasheet here: This is probably the clearest 3.3V source I have seen so far. Note how it sits within ...

2

First, if your "LM2596" is the usual \$1 module from aliexpress which has counterfeit LM2596, "cost-optimized" inductor which saturates on every peak, and no-name general purpose caps totally unsuitable for switching supplies, place it where it belongs: in the recycling bin. As an alternate solution you can run it at rated current until ...

3

A resistor can be used in two very different ways to reduce heat load on a three-pin regulator chip: simulate this circuit – Schematic created using CircuitLab The second circuit cannot be used in your application because the regulator chip has a maximum input voltage of 35V and can't handle 44V. The first circuit can be used only if the load is ...

1

This circuit should do what you want. The Zener diode and transistor are an approximate voltage detector for about 10V nominal. By using a discrete circuit we can guarantee the performance down to 0V, which is not always possible when using a chip, since it may misbehave outside the minimum voltage for proper operation. Calculate the dissipation of R1 and ...

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The maximum input voltage on the LM7812 is 35V, but we should operate at about 75% of the maximum rated voltage to be on the safe side. You need 500mA current so according to the rule of the linear regulator, the input current will also be 500mA which is flowing from R1 as well. If you use a 5W resistor, the maximum voltage drop it can handle is = 5W/0.5A = ...

0

Since the input current on ON/OFF pin is low (<30uA) and since there is an inherent hysteresis on this pin: You can simply apply the input voltage through a voltage divider: simulate this circuit – Schematic created using CircuitLab if you want to control the hysteresis you can add a feedback from the output voltage like this (this is applicable ...

1

i want it turn on for example when input voltage is above 10 volt and turn off when input voltage is below 10 volt . I see what you mean - the control is inverted and doesn't easily lend itself to adding a simple potential divider however, it might be a mistake not to consider that some level of hysteresis is required. For instance, when the voltage is ...

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It oscillates with both 10 Ohms and 100 Ohms at 11V/1A. The oscillation can be eliminated with a 220nF capacitor at the indicated location.

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By increasing the resistor to 100 ohm all the output current is through the transistor so the regulator is out of the circuit. Change the resistor back to 10 ohm this way the transistor will conduct only when the output current is greater than 50mA. If you increase the resistor to 22 ohm you may get only 25mA through the LM317

3

I had similar problem when trying to stabilise 6,3 V for tube amp filament. With no load, everything is perfect, under the load, voltage dropped significantly. There are two problems: Voltage drop IN-OUT: see datasheet - there is about 1,5 V drop in 20 mA out current but 2,3 V drop on 3 A. How "hard" is your V-in source. My transformer dropped ...

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SPDUs can contain DC/DC converters, but don't have to; it is not their main purpose to convert power. SPDU's functionalities differ, but their main purpose is simplifying and monitoring power connections. You can read about them here. There's even an executive summary.

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To the right of the current knob is a knob to select voltage. It is set to 6V in your picture. Rotate that knob so that it points to "3-15" or whatever the right most marking is. That is the variable voltage setting. With the selector knob set to the variable range, the coarse and fine voltage knobs will set the output voltage.

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Have you configured pin D0 as an input in the software? If D0 is inadvertently set as an output there could be an issue where the SW420 signal is shorted.

-1

Such output caps are for Smoothing for very quick current droops. and ceramic caps for even much faster current noise in the regulation line such as if the sensing element is not to be perturbed by linearity loss

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Now I hook up a 3.3V supply directly to the VOUT of the MCP and let the VIN floating You are misusing the regulator outside of its intended regime of operation; the answer is not to do that; not only does it yield undesired results, it may over time cause damage. One specific specification you are violating is the statement in the Absolute Maximum Ratings ...

1

If I use what appears to be a 100mh (by comparing it with 100mh coil images online) and it turns out to be a different value, what will be its impact on the performance or other factors You'll probably find that 100 mH is far too much for most applications but, you never said what application it is so maybe it's secret. I'd try it on a dummy representative ...

0

What if I connected my Zener diode with my load in series? This is another useful application of the Zener diode acting as a voltage-stabilizing element. We can figuratively name it voltage shifting. Here are a few explanations of this circuit trick. "Battery". First, we can think of the Zener diode as a constant voltage source ("battery"...

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What if I connected my Zener diode with my load in series? This is another useful application of the Zener diode acting as a voltage-stabilizing element. We can figuratively name it voltage shifting. Here are a few explanations of this circuit trick. First, we can think of the Zener diode as a constant voltage source ("battery") that is connected ...

2

A switcher will almost certainly be better. You should be able to find a buck module that will drop 18V down to 5V. Shop carefully -- there's older design modules out there that aren't very efficient. You should expect 80% to 95% efficiency. If you're willing to go for it, you can build a switcher onto your board from one of the many chips out there. If ...

0

If you are worry about the linear power supply's low efficiency (while staying very low noise), which will makes it very hot, you can use multiple linear power supply in series, for example stage 1 convert 36V to 24V, stage convert 24V to 12V, stage convert 12V to 5V. The Zener will work, but under extreme temperature conditions, the Zener may fail due to ...

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This is a typical application diagram of the LT3014: The regulator regulates the output voltage by regulating its pass transistor (between IN and OUT) such that at the ADJ pin there's a voltage of 1.22 V ("ADJ pin voltage" in table on page 3 in the datasheet). The output voltage gets to the ADJ pin through a voltage divider (the 3.92M and 1.27M ...

0

I think the problem has been solved as of yesterday. I noticed a voltage of about 30mV in the ground of my circuit board. For the same reason the regulator seems to be raising the voltage above 3.3 by taking the ref voltage. I think this is caused by the ground touch of one of the solders I made on the circuit. Because I did not have a problem with my other ...

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