HIGH CURRENT DC DEVICES TIP122

  


The Controlling Multiple LEDs Tutorial uses the 2N3904 small current transistor. This works well for controlling additional relatively small current devices with the Arduino. You may want to use the Arduino to control a DC powered device that draws more current that the 2N3904 transistor can supply. A solution for this situation is to use an NPN Darlington Transistor designed for medium power linear switching applications. In this tutorial we will use a TIP122 transistor, which can power devices up to 100VDC at 5 Amps. This can be used to power devices such as motors, solenoids and fans, where the only necessary operation control operation is ON and OFF (see the H-Bridge Tutorial for bi-directional rotation and speed control of DC motors.)

The circuit is identical to the 2N3904 transistor circuit - the base of the transistor (PIN 1) is connected to the Arduino output pin (D6) through a 1K OHM resistor. The emitter (PIN3) is connected to ground and the collector (PIN2) is connected to one end of the coil of the device being driven (in our example we have a 12VDC Solenoid connected). The other end of the coil is connected to the +12VDC external power supply (the ground from this power supply is connected to a common ground with the Arduino - this is necessary for the transistor to function). It is very important to put a diode across the coil of the device being powered to protect the control circuit from a potential voltage spike that can be created when current is released from the device being powered.

PC817 High Density Mounting Type Photocoupler

An optical isolator is known as a device which enables transmission of an electric signal by making use of the signals induced by light. The theory behind this is that coupling needs to be done between the insulation of input and output of a circuit board or a single wire which makes use of these principles. The basic purpose of any kind of optical isolator or a photo coupler is to make sure that any high changing voltages do not damage the components. This is done via carefully designed and manufactured photo couplers which are sold by a couple of different electronics manufacturers out there. Most known manufacturer of photo couplers is Sharp. If you’re interested in upgrading your circuitry with a device like this, you will need to do some proper researching first. Since this is a component which is intended to protect your devices, it’s important to know exact specifications of the photo coupler you’re looking for. Fortunately, this is no problem since there are plenty of datasheets specific to PC817 photo couplers which you can get for free online and get all the information you need. For starters, you can visit HQEW.net ’s official website where you might find some decent information on how can you order their products, but it’s more important for you to test your circuits first to know what numbers need to be matched and to what extent. Tolerances are very important here and this research will help you save cost on future purchases.