the percentage of total power supply current going through the short depends on the particular circuit design
you can be assured that KVL and KCL must stand true
Not always. It depends where in the circuit the short is. Look at the simple amplifier circuit below.The percentage of the total power supply current is divided up and the SHORT will have 98% of the current , right?
If there is a short between the base and emitter of the transistor, then the total current through the circuit will only be about 1% of what it should be, but all of that current is flowing through the short.
If the short is between the base and collector of the transistor, then the total current drawn by the circuit is nearly double what it should be, but less than 1% of that current is flowing through the short.
The circuit I showed normally draws about 2mA from the battery.
If there is a short between the base and emitter, then the circuit only draws about 20uA from the battery, and 99.9999% of that goes through the short.
If there is a short between the base and collector, then the circuit draws about 4mA from the battery, but only about 20uA flows through the short.
The circuit I showed normally draws about 2mA from the battery.
No. The total current is 20uA. All of that current goes through the short, so the current through the short is 20uA.1.) 20mA - 20uA = the 99% shorted current?
Yes.This gets me so confused about shorts, because a short can go either way 99% or 1% of the total power supply current
No! A short has no resistance so there is never any voltage across it.The Voltage across the short would be if it's 99%? would the voltage be 99% of Vcc?
No. Same reason.The Voltage across the short would be if it's 1%? would the voltage be 1% of Vcc?
In this circuit, a short between collector and emitter would draw about 4mA.Can a short draw more current that 2ma? what kind of short would draw more current than the total power supply current?
When there is a short circuit, the total current may go up, go down, or stay exactly the same.
When there is a short circuit, the current through the short may be very high, very low, or anywhere in between.
If something is wrong, do not assume there is a short circuit. The problem may be caused by a short circuit, an open circuit, a faulty part, or something else.
When a piece of equipment that was working suddenly stops working or develops a fault, the problem is most likely not cause by a short circuit.
The Voltage across the short would be if it's 99%? would the voltage be 99% of Vcc?
No! A short has no resistance so there is never any voltage across it.
The Voltage across the short would be if it's 1%? would the voltage be 1% of Vcc?
No. Same reason.
.1.) 20mA - 20uA = the 99% shorted current?
No. The total current is 20uA. All of that current goes through the short, so the current through the short is 20uA
What if the faulty stage normally only takes 10% of the total supply current?Mostly the Faulty stage or network will either be 99% of the total power supply current or 1% of the total power supply current right?
An open circuit may cause the total power supply current to go up or down.if the Faulty stage is an Open current, the Total power supply current won't go UP or Down Right?
No, there can be other reasons.Only A short circuit will cause the total power supply current to go UP or Down right?
The total power supply current is not 20mA anymore. It's 20uA because of the short.So the Total Power supply voltage is not 20mA anymore it's 20uA because of the SHORT?
The other stages/networks/branches are going to have nanoAmps of current because the short has 20uA of current. Its hogging all the current.THe other stages/networks/branches are going to have nanoAmps of current because the SHORT has 20mA of current, its hogging all the current right?
An open circuit may cause the total power supply current to go up or down.
The total power supply current is not 20mA anymore. It's 20uA because of the short.
When there is a short, the tech at my work will always reference the 100mA at the total current of the circuit. The tech will measure the current from a Resistor tied to Vcc to know what that stage is being Feed. Mostly It will be microamps because the SHORT is hogging all the current right?
As your power supply voltage is 12v(for example), So the current from your power supply will be 12/low or zero= very high. For this reason you can not connect your circuit to your power supply. There are special type power supply which can understand that, threre is a SHORT in its terminal and they automatically reduce their voltage so that a high current can not flow. Then what current will flow? There is a knob in the power supply to set that.A short from Vcc to Gnd is easy, just check continuity between Vcc and Gnd if they are common they are shorted
Ya, but which stage of the circuit is the Short from Vcc to ground?
The Tech at my work find shorts this way:
1.) Measures the Currents Total from the power supply
2.) Then measures the current from each resistor that is tied to a Vcc supply voltage in each stage
If the Current total is 100mA out of the power supply, So Kirchhoffs Law states that current needs to Equal it's loop or Current Total
If you measure the current from each branch or resistor that is tied to Vcc then you will know how much current is being Feed to that stage of the circuit
When there is a short, the tech at my work will always reference the 100mA at the total current of the circuit. The tech will measure the current from a Resistor tied to Vcc to know what that stage is being Feed. Mostly It will be microamps because the SHORT is hogging all the current right?
So if the total current is 100mA
You measure The Resistor tied to Vcc of each stage, you will mostly get 10uA or 50uA
he will always say where is there rest of the of the current going?
100mA - 10uA =
100mA - 50uA =
I just have a hard time finding where the Rest of the current is going to lead you to the SHORT or whats SHORTED , How do you find where the Rest of the current is going?
The stages that don't have the SHORT, will have very low current in microamps
The Stage that has the SHORT will have 97% of the Total Current referenced from the power supply Total Current?
The other 3% will be in microamps for the other stages that don't have the short?
Some stages have a series resistor. Some stages do not have a series resistor.
Yes, by measuring voltage drops of supply traces with a mV meter. If the board doesn't use power planes, you can usually localize the component drawing excessive current.Is there another way to Find a Vcc to ground Short besides increasing the power supply current to 1A?
Yes why is that some stages have a series resistor and other stages don't have a series resistor , why is that?
Do I have to Disconnect each stage of the circuit one by one from Vcc?
Not necessarily. Did you read the answers to your previous question?How do I know which stage of the circuit is the faulty stage that is causing Vcc to ground short?
Do I have to Disconnect each stage of the circuit one by one from Vcc?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?