56

You can't float everything without an isolation transformer - the neutral will be connected to ground at the entry into the building. For safety any class I equipment does need to remain grounded, in my lab I have an isolation transformer only for the equipment under test, the scope and power supplies still have the case grounds, and are tolerant of the ...


38

I don't have a complete answer for you, but the 8080 was one of Intel's first chips to use an NMOS process rather that the PMOS process of the 4004, 4040, and 8008 chips. In NMOS, the substrate must be the most negative point in the entire circuit, in order to make sure that the isolating junctions of other circuit elements are properly reverse-biased. So, ...


35

No. A linear regulator works by burning off excess voltage as heat, therefore current in equals current out. The linear regulator is essentially throwing away the excess energy in order to regulate, rather than converting it to the output. You need a switching regulator if you want to take advantage of power in equals power out in order to convert a high ...


28

RL1 is a relay, a type of electrically-actuated mechanical switch. The swirls are the relay's coil, and the two lines indicate that it's wrapped around a magnetic core. The thing labelled N/O and N/C is also part of the relay; N/O is "normally open", which means that switch contact is open, or disconnected, when the relay coil is not energized. N/C likewise ...


25

Negative on the outside of the barrel connector, positive on the inside of the barrel connector. It is the standard method of showing the polarisation of the barrel connector. The positive pin is usually (as in this case) the inner contact, and negative is usually the outside of the barrel. If you look at the image, it shows a surrounding area labelled "-",...


24

This is neither Kosher nor Halal. It should actually be explicitly forbidden in the Electrical Engineering code of ethics. Some certification standards explicitly frown upon this. Besides the wires probably being extremely under-dimensioned for the delivery of power, using narrowly-defined standard connectors for non-standard uses is a sure way to cause an ...


23

Twisting wires reduces the magnetic loop area of the wires, this has two implications: Reduced susceptibility to noise from magnetic fields, with twisted wires an a smaller magnetic loop area, external magnetic fields will induce less current in the loop made by the wires than straight cables. Reduced magnetic radiation from loads that are switching. A ...


16

This is a fiber optic splicebox. It is a weatherproof enclosure where two (or more) ends of fiber optic cables are connected. Yes - electricity poles also carry optical fiber for control of the network and often internet access.


15

It's a junction box for fiber optic cables. Here you can buy a similar one.


15

Most certainly a surge (or in-rush) current problem. Electric motors, at start-up (when they are not spinning yet) and especially when driving a load (like turning the pump's impeller against water) draw enormous short-term (surge) current. This surge quickly dies out once the motor "gets going". From wikipedia When an electric motor, AC or DC, is first ...


14

Is there a reason this schematic uses an op amp (AD8031) for the reference voltage of the op amp (AD8544) filter when the voltage divider already brings down the voltage anyways? The usual reason to use an op-amp to buffer a divider like this is to ensure the reference voltage doesn't change if whatever it's connected to sinks or sources current. Can the ...


14

They’re adjustable power resistors. You loosen the screw and move the ring to or fro to get the resistance that you want and then tighten the screw. Probably a dummy load for various supply rails.


14

A quick look at the Radio Museum pictures and descriptions makes it look like it ought to be fairly easy to hook up. Here is the picture of the connections from the Radio Museum: You provide it with 4V through the jacks on the left side. You could use a battery pack with 3 normal AA or C cells in series. That's the easiest way, and will probably sound ...


13

Is there a reason ... Yes. The two 10k reisistors give the voltage reference an impedance of 5k. This means that if the current drawn from the reference changes by 0.1 mA that the voltage of the reference would change by 0.1m x 5k = 0.5 V. This would be a very unstable reference. The op-amp buffer fixes this. The output impedance of the buffer is close to ...


13

If this is not possible, is there an existing type of cable that can achieve this (3 power leads and a ground), or will I have to solder my own? Cables will do whatever you want them to do, they carry current from one point to another. The biggest concern would be if someone accidentally plugged the USB cable into a regular USB device which would ...


13

To answer your comment to Puttafish, Why do they draw it on the power supply? Why not near the connector? The connectors are purchased with no polarity assignment. It's up to the PSU designer what the polarity is or if it is AC. Thus it makes sense for the PSU builder to label the polarity on the PSU along with all the other technical information. There'...


13

THIS CIRCUIT WILL KILL YOU Or your family Or your friends The capacitor MUST be X or Y rated for AC mains use. If it is getting hot you are using the wrong cap. Regardless of what formulae and calculations say, if the resistor is getting too hot you must use a larger wattage one or cool it better. The same applies to the zener diode. This circuit ...


13

It's a "power" inductor because it needs to carry a significant amount of DC current. Connecting the windings in parallel gives you the same inductance as either winding alone, but with twice the current capacity and half the DC resistance. It's exactly equivalent to a simple coil with the same number of turns, but twice the cross-sectional area of the wire.


12

20 watts delivered into a hand-cranked generator (enough to deliver 10 electrical watts after conversion losses) could be managed all day by a fit and motivated person. This would employ all of your arm muscles. However, you'd need reasonable length cranks, comfortable handles, a good secure mounting for the generator, it's not something you'd nonchalantly ...


12

NO = normally open contact NC = normally closed contact Normally open (NO) contacts connect the circuit when the relay is activated; the circuit is disconnected when the relay is inactive. Normally closed (NC) contacts disconnect the circuit when the relay is activated; the circuit is connected when the relay is inactive. All of the contact forms involve ...


12

C2, D5, D6 form a charge pump to produce the negative voltage required to allow the opamps to get down to the negative rail, it is a fairly popular trick when you want a supply that can vary right the way down to 0V (Which is otherwise a surprisingly hard thing to pull off). Charge pumps require the input to be AC (or at least pulsating DC).


12

No, it won't step up current. You can think of a regulator as a resistor that adjusts it's resistance to keep the voltage stable. However, you can buy DC to DC converters that 'boost' the current. But DC to DC converters are usually called by what they do to the voltage, not the current. A boost converter 'boosts' or steps up the voltage from a lower ...


12

You need two back-to-back P-channel MOSFETs for each power input. Here is an example from an Atmel eval board, though you'll want to scale up the MOSFETs considerably, and maybe reduce the resistor values to something like 10K: The VCC_USB input is dominant if both are present (in other words, if only one supply is present, that one will be used, if both ...


12

What are those parallel soldered-traces on the PCB traces? They are traces where some of the soldermask has been removed in order to allow solder to build up to improve the current capacity of the trace. The reason they left the narrow parallel lines of soldermask is so that the solder distributes itself more evenly across the width of the trace. ...


11

It seems you are making several beginner's mistakes in your understanding and application. You are using the LM2956 5.0 which is the 5 V version. This will output a regulated 5.0 V subject to meeting certain conditions including the required input voltage and current and having a load drawing between the rated minimum and maximum. The 3 A maximum output ...


11

What is the right way to float my home lab? If you want to make measurements that are isolated from ground, the only way to do this is with an isolation transformer if your scope is not isolated. There are very few reasons to do this, a high voltage setup would be one reason. Some AC measurements would be another. Differential probes are best. Do I ...


11

Contrary to popular belief this does work, but the P7805 is a DC to DC converter and it can sink current. A regular 7805 voltage regulator requires a negative supply, this does not. Here is a excerpt from the P7805 datasheet: Source: https://www.cui.com/product/resource/p7805-s.pdf


10

The choice of 19 volts is because is it comfortably below 20 volts which is the maximum output voltage of power supplies that can be certified as LPS (Limited Power Source) with non-inherent power delivery limits. If you can keep at or below 20 volts, the whole safety certification thing becomes easier and cheaper. To make sure you're within the limit ...


10

We've given your photo to the forensics lab and they suspect that it is a fibre-optic data cable using the electrical power distribution poles as the cable route. Photo 1. The enhanced image. The incoming cable. The cable clamp. The down-feed to the junction box where tap-off and through connections are made. The cable out to the next stage. The outgoing ...


10

On low voltage power systems (<1000V), ships use insulated neutrals to protect the integrity of the power system. On land, a grounded neutral is used. Any ground fault (hard or instantaneous) will cause breakers to trip or fuses to open. At worst, you are in the dark. The offending breaker would be easy to find. But at sea, a power outage can cause ...


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