Flyback transformers, also called line output transformers, are used to supply power to electrical circuits and to generate high-voltage signals at a high frequency. Flyback transformers are power inductors. They take energy from an electrical source such as a battery, then briefly store the electrical energy in the magnetic field created by coils wrapped around a ferrite core. The energy is then transferred to a circuit to power it.
Find the two wire coils located on the back of the flyback transformer. One is the feedback coil, the other is the primary coil. They should be covered and 'potted' inside the flybacks. If they are not insulated, attach a plastic coil form to them. Wrap plastic sheet around the plastic coil form, then cover it in electrical insulating tape.
Find two pairs of interconnected wire coils attached to the horseshoe-shaped connection pins. This is done by testing the fly-back pins. There may be more than two pins on a single curve of a transformer coil. Measure the resistance of each wire with an ohmmeter to find the high-voltage output pins, which will have a resistance between 100 to 1000 ohms compared to single-digit readings and less for the others. These are the coiled wires that are going to have wire attached to them.
Wind four pieces of the #16 gauge insulated wire four to six turns around the coil of the flyback. Glue them in place. Wrap insulation tape over the connection. It doesn't matter which way you wind them, as long as you wind both of them in the same direction.
Inductance in parallel is normally one-quarter that of series wound coils on the same core and it looks like this is true of these inductors so, if the series inductance states 8.8 uH, one winding will be 2.2 uH - remember that two parallel windings (closely coupled) have exactly the same inductance as a single winding with the same turns. Adding a second switch to the high-side of a conventional single-switch forward or flyback converter design reduces electrical stresses on the MOSFETs, improves efficiency, and cuts EMI. Flyback Driver Circuits High Voltage with a Television Flyback Transformer. Circuit 1: Ultra simple Single Transistor flyback driver circuit. I am able to carry out the more powerful single transistor driver experiments. As expected, there was a significant improvement over the 50W lightning transformer driver.
Connect the wires at the center-tap terminal of the flyback located near the coils on the back of the transformer. Insulate the connection with electrical tape. Hook them up to the circuit in any polarity or position. If you don't hear humming electricity, switch the leads to reverse the polarity of one of the coils.
Mount the transistor onto the large heat sink. The transistor mounting kit comes with a mica isolator, thermal compound, mounting bracket, screws and plastic spacers. Insert the plastic spacers between the mounting bracket screws and the transistor. Place a mica isolator between the transistor and the heat sink. This protects you from accidental shock. Place thermal compound between the transistor case, the mica isolator and the heat sink. Tighten the screws to secure the mount.
Connect the flyback transformer to the transistor, at the top of the which are B, C and E terminals. B is the base terminal, C is the collector terminal, and E is the emitter terminal. Connect one of the feedback coil wires to the B terminal of the transistor and solder into place. Connect the negative end of the primary coil to the C terminal at the top of the transistor and solder into place. Place a new wire on the E terminal and solder into place. Lead the end of the E wire to the negative terminal of the battery and secure it to the battery terminal.
Insert the wires of the 5W resistor to the printed circuit board and solder them into place. Position the 1W resistor on the circuit board so that the positive end of the 1W resistor leads to the negative end of the 5W resistor. Solder the 1W resistor wires or pins to the printed circuit board. Attach the positive end of the feedback coil to the wire of the printed circuit board that leads from the 5W resistor and the 1W resistor and solder into place.
Connect the positive end of the primary coil to the positive end of the battery and secure it. Solder a wire to the positive end of the 5W resistor. Lead this wire to the positive terminal of the battery and secure it.
Tip
Place a small layer of flux on the terminals and the wire before soldering. Add only a small amount of melted solder wire to solder them into place.
Warning
Flyback circuits transmit a lot of high-voltage electricity and can create fires or shock you, so use with caution.
I do not have an L293NE or SN754410 H-bridge chip, but I need to drive a motor in 2 directions using only a pin on a micro-controller to switch between them. I was originally driving the motor with a single NPN transistor, which gave me enough speed and torque for my project (it's a 4 wheel drive robot). However, it became clear that I would need both forward and backward movement. I drew up a simple circuit diagram using a PNP transistor to switch the flow of the motors, however, when I created the circuit, there was no movement when pulsing.
Here is the circuit diagram:
What exactly is wrong with my circuit here?Why does it do nothing as opposed to maybe frying the board or working in someway?
Most importantly:How can someone drive a dc motor in 2 directions with transistors? Will my way work or would you need to try something else to get it to move clockwise and counterclockwise?
2 Answers
Simple Flyback Driver
$begingroup$The two leads of the motor are shorted together so no matter the state of the transistors, the current will always flow around the motor instead of through it.
Single Transistor Flyback Driver For Macbook Pro
For example, if the 'Switch Motor' signal is pulled HIGH, then the current completely bypasses the motor as shown below:
When the 'Switch Motor' signal is pulled low, nothing happens. The base of the upper transistor is reverse biased, so it is in the OFF state and no current flows. Unless you meant for that transistor to be a PNP instead of an NPN, then current would flow from 5V to GND but it would still bypass the motor. Either way, the result is no motion from the motor.
I recommend studying how a classic H-bridge functions. They're relatively simple circuits, and doing so will also teach you about flyback diodes to protect your circuit. Here's a good explanation.
Its probably not the answer you want, but depending on the scarcity of components in your area, a very rudimentary H-bridge can be built with 2 relays:
simulate this circuit – Schematic created using CircuitLab
p.s.: good thing is, shoot through is practically impossible.
Wesley LeeWesley Lee