Simple DC Electronic Fuse Circuit

Is anyone sick of the fuse blowing? This one can be helpful!

DC electronic fuse circuit is like small hero for ones electronics.

It protects from big current going crazy.

Old fuse? You break it then one may need new one, but this one?

It uses smart components always checking current.

If current is too much it stop power fast without damaging anything.

Circuit Working:

Parts List:

The DC electronic fuse can work forever no need to change it.

Just press the start/reset button S1 and one will find the circuit works again.

When S1 is pressed C106 and T1 turn ON then current passes to load using T1 and resistor R2.

Even after one leaves the button current still flows if it is not too low.

But if current go other way through transistor T2 2N3055 and R2 then current in T1 goes down.

T2 and R2 are part of this fuse to do that.

If voltage on R2 become bigger than T2 base emitter trigger (about 0.7V) then T2 start working and skips T1.

R2 should not be less than 0.2 ohm in that way the fuse current × R2 = 0.7V.

After T2 skip T1 current in T1 become low and T1 turn OFF.

Then voltage on R2 also drop so T2 stop too and circuit becomes OFF

To make it work again one should press the S1 button again.

R1 resistor value depends on power voltage and just take supply voltage × 1k to find it.

Connect this fuse circuit to PLUS side of the load.

Whole circuit does not drop much voltage it does under 1V only.

Formula:

This below mentioned formula is used for DC electronic fuse:

R1 = V * 1 kΩ

• R1 is resistor that limits the current which goes in line with the load (thing one wants to protect)it measure R1 in ohms (Ω).
• V is the voltage from power supply where the fuse protect this voltage and it measure V in volts (V).
• 1 kΩ is fixed resistor number it mean 1,000 ohms.

Why this formula?

It help find right resistor value R1 for fuse.

This resistor stop too much current if overload or short circuit happen.

Note:

How one uses this exactly can change it depend on the circuit and what job R1 is going to function.

How to Build:

To build a Simple DC Electronic Fuse Circuit follow the below steps for connections:

Get Circuit Board Ready:

• First take one good board where we need to put all the circuit parts.

Put Parts on Board:

• Place C106 T1, transistor T2, resistors R1 and R2 and the start/reset button S1 on the board.
• Follow the circuit diagram to put parts in right way.

Connect All Parts:

• Solder each part on board same like in diagram.
• Be sure all wires and pins connected correctly.

Connect Power Supply:

• Join power supplies positive (+) to PLUS side of the load.
• Negative (–) goes to GND of circuit.

Wire the Button (S1):

• One side of button S1 connects to power supplies +.
• Other side connects to gate of C106 T1.

Connect Resistors:

• Put R2 in series with T1 and load.
• R2 must be minimum 0.2 ohms.
• Find R1 using this formula: R1 = V × 1kΩ (V is supply voltage).
• Connect R1 in right place.

Connect Transistor T2:

• Connect T2 in parallel with R2 and T1.
• Check emitter, base and collector is connected the right spot like in diagram.

Test the Circuit:

• Before fixing everything test if fuse works good.
• Be sure voltage drop stay under 1V.

Final Setup:

• If test is OK fix all wires and parts on board tight.
• Put whole circuit inside small box to protect it.

Try the Fuse:

• Give power to the circuit and press S1 button.
• See if fuse turns ON and OFF when current go high or low.

Note:

• Always check the circuit diagram while constructing.
• Be careful when using soldering iron and working with electricity.

Conclusion:

Big benefit of Simple DC Electronic Fuse Circuit is, it can give exact and adjustable protection.
Also no need to replace parts one can reset and use again.

People use this fuse in many places where overcurrent protection is important like power supply, motor control and car electronics.

References:

Why and How to Effectively Use Electronic Fuses to Protect Sensitive Circuits