How to make reverse polarity protection without voltage drop
Typically, a diode is used to protect against polarity reversal. The solution is very simple, but has a number of disadvantages: even if you use a Schottky diode, you cannot avoid a drop of at least 0.4 V. Also, at significant currents, about 10 A, the diode begins to heat up and cannot do without a radiator, and therefore the size of the device will increase.
To avoid these drawbacks, a more intelligent circuit can be used that can be used to both power a load that is sensitive to incorrect polarity connections. Same for the battery charger.
You will need the following parts
- Two 1 kOhm resistors - http://alii.pub/5h6ouv
- Relay 10 A 12 V - http://alii.pub/5y3wwl
- Red and green LEDs - http://alii.pub/5lag4f
- Diode 1N4007 -
Scheme
The protection circuit is incredibly simple and if you do not take into account the signal LEDs, consists of a diode and a relay. You will learn about the operation of this scheme below in a specific example of use.
Do-it-yourself protection against polarity reversal without falling
The circuit is assembled by hanging installation for clarity.
Single-core copper wire is used as power buses.
Using a circuit for a load
If you use a circuit to protect a load, then the source is connected to the left side of the circuit, and the load to the right. If the power is supplied correctly, current will flow through the diode to the relay and it will switch the contacts, supplying voltage to the load.
Proper operation will be indicated by a green glow. LED.
If the power is supplied incorrectly, the relay will not turn on, since no current will flow through the diode. Incorrect connection will be indicated by red Light-emitting diode.
Using the charger circuit
If you use a protection circuit for the charger, then it is connected on the right, and the battery on the left.
The work is just as simple: even in a completely discharged battery there is a voltage of about 9 V, which is enough to turn on the relay. And if the battery is connected to the charger correctly, the relay will close the contacts. If not, then the relay will not work and the red light will turn on. Light-emitting diode.
