E
Eric
Guest
Try this out you need five parts including two resistors.
But you need to draw it first, with the following five components
Thyristor (SCR) C106C
Power transistor 2N3055
Low ohm resistor, I will say one Ohm (needed for the current to be set)
Resistor to trigger the gate of the thyristor.
One normally closed push "on" switch.
Now for the circuit
Going from the power supply to the load
Draw a line to the anode of the SCR from the cathode goes the one Ohm
resistor to the load.
The collector of 2N3055 goes to the (power supply) - anode of the SCR, the
base goes to the SCR cathode - one Ohm junction & the emitter of the 2N3055
goes to the one Ohm - load junction.
You need something to activate the fuse (reset it), from the gate of the
SCR, a resistor via a "press on" switch to the anode - power supply
junction, make the resistor about 1K for every volt of the power supply (Max
60 Volts)
==========================
Now hear is how it works in theory,
When the current going through the 1 Ohm resistor exceeds the trip current
of this electronic fuse, the 0.7 Volts across the 2N3055 turns the 2N3055
transistor on, that shorts out the anode-cathode of the SCR, below the
holding current of the SCR and that turns the SCR off, causing the
electronic fuse to trip and turn off.
==========================
How ever this circuit found in "Elektor Electronics" magazine July-August
1980, page 7-34, does not work,
I think the base-emitter current needed to turn the transistor on has been
"shorted" out by the 1 ohm resistor, so it never gets to turn the 2N3055 on
and short out the SCR and turning the fuse off.
does anybody agree with that?
But you need to draw it first, with the following five components
Thyristor (SCR) C106C
Power transistor 2N3055
Low ohm resistor, I will say one Ohm (needed for the current to be set)
Resistor to trigger the gate of the thyristor.
One normally closed push "on" switch.
Now for the circuit
Going from the power supply to the load
Draw a line to the anode of the SCR from the cathode goes the one Ohm
resistor to the load.
The collector of 2N3055 goes to the (power supply) - anode of the SCR, the
base goes to the SCR cathode - one Ohm junction & the emitter of the 2N3055
goes to the one Ohm - load junction.
You need something to activate the fuse (reset it), from the gate of the
SCR, a resistor via a "press on" switch to the anode - power supply
junction, make the resistor about 1K for every volt of the power supply (Max
60 Volts)
==========================
Now hear is how it works in theory,
When the current going through the 1 Ohm resistor exceeds the trip current
of this electronic fuse, the 0.7 Volts across the 2N3055 turns the 2N3055
transistor on, that shorts out the anode-cathode of the SCR, below the
holding current of the SCR and that turns the SCR off, causing the
electronic fuse to trip and turn off.
==========================
How ever this circuit found in "Elektor Electronics" magazine July-August
1980, page 7-34, does not work,
I think the base-emitter current needed to turn the transistor on has been
"shorted" out by the 1 ohm resistor, so it never gets to turn the 2N3055 on
and short out the SCR and turning the fuse off.
does anybody agree with that?