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I have a circuit where I want to have a constant current of 2mA through a variable resistor. I've been told that I could probably use a LM317 as a current regulator, with one resistor on the ouput. But I've read some places that the LM317 takes minimum 5-10mA load to function correctly. How can I achieve a constant current output of 2mA when I don't know the resistance of the variable resistor? The input voltage is about 2.755V. Output voltage doesn't matter, just the current. Here's an image to my feeble attempt at a schematic: The LM317 with the single series resistor between output and adjust input is actually a fixed current source, not a current limiter. You don't need the LM317 to create a current limiter, a few discrete components will do: For a limiting at 2mA you select a 330 Ω resistor for R S E N S E . If there flows 2mA through it Q2 will start to conduct and reduce the base voltage of Q1, so that its current is cut off. edit (re changed question) ...

 At this point is a Solar Charger Circuit to is used to charge information Acid otherwise Ni-album batteries using the solar energy power. The circuit harvests solar energy to charge a 6 volt 4.5 Ah rechargeable battery in favor of various applications. The stallion has Voltage and Current supervision and terminated voltage restrict sour facilities. Circuit uses a 12 volt solar panel and a changeable voltage supervisor IC LM 317 . The solar panel consists of solar cells each one rated on 1.2 volts. 12 volt DC is presented from the panel to charge the battery. Charging current passes through D1 to the voltage watchdog IC LM 317. By adjusting its Adjust pin, output voltage and current can subsist regulated. VR is placed amid the adjust pin and ground to provide an output voltage of 9 volts to the battery. Resistor R3 confine the charging current and diode D2 prevents discharge of current from the battery. Transistor T1 and Zener diode ZD conduct yourself having the status of a stop ...

You most likely know that LM317 IC is applied as an practical provide regulator, but did you know it can be applied as an audio amplifier? This is a Low power Amplifier LM317 Simple Audio Amplifier Circuit a audio  designed with LM317 that offers a optimum probable 1W audio strength.  LM317 Simple Audio Amplifier Circuit Diagrams : LM317 Simple Audio Amplifier Circuits Utilization a amazing heatsink for the LM317 IC and modify the 5K various resistor so that you have 4.5V on 10Ω resistor (or LM317 pin 2, Vout).

This circuit is a battery eliminator 1.5 V , that is, a power supply of 1.5 volts , low consumption that takes as input the output of the USB PC or notebook. The power adapter is simple , it converts the voltage from 5V to 1.5V USB ports , using the popular LM317 IC and a few other components . To be exact this circuit uses only three components , one is the LM317 , R1 = R2 = 470 ohm and 100 ohm .  Eliminator 1.5 Volt battery using LM317 Circuit Diagram

A very simple universal battery charger electronic project can be designed using the LM317 voltage regulator and some other electronic components . As you can see in this schematic circuit this charger has extreme few components , but is doing a very good job . When power is applied to the circuit the SCR1 is off, so there is no bias-current path to ground. Universal Battery Charger Circuit Diagram: The LM317 is connected to the battery through diode D1, limiting resistor R1, and bias resistor R2. The D1 diode is used to prevent the battery from discharging through the LED and the SCR when power is removed from the circuit. When LED1 is on, the circuit is in the voltage-regulating mode and when LED1 is off, the circuit is in the current-regulating mode.

This is a basic,  Universal Power Supply voltage regulator circuit using an LM317, 3-terminal regulator in a TO-220package. The Universal Power Supply output voltage can be set to anywhere in the range one.5V to 30V by selecting resistances. By using a potentiometer, R2, as of the resistors you can dial up the output voltage wanted. Either AC or DC input can be supplied to the PCB by a socket or terminal block. Connection can be either way around. This is because they have provided a bridge rectifier on board. The input DC voltage to the regulator must be at least two.5V above the necessary output voltage. An off/on switch is provided. For lots of applications (say 12V at 60mA) a heat sink won't be required. The LM317 will provide slightly higher output voltages than 30 volts. However, for most hobbyists over 30V won't be needed. So to make a small PCB they have used some electrolytic capacitors rated to 35 volts. To be safe for continuous operation the maximum input DC voltage...

Lead Acid Battery Charger circuit is highly recommended to recharge battery. And recommended that maximum voltage 24V 7A battery, so you can recharge a battery simultaneously. Battery Charger has been little use of several components such as diodes, electrolytic capacitors , transistors , resistors, and also for strengthening of the voltage and current stresses. And also do not forget to lowering electric voltage 220V to 20V-35V 5-10 Ampere suitable for Lead Acid Battery Charger circuit.  List of components for the circuit Lead Acid battery : R1               = 1 Ω 2w R2               = 100 Ω R3               = 220 Ω R4               = 10K Ω Trim D1 - D5       = IN4004 Q1               = BC547 IC 1          ...

This is the simple RF Transmitter using LM317 Circuit Diagram . Already we saw that the LM317 has hundreds of utilities besides a voltage regulator , how in this article of a audio amplifier with the LM317 . Now that circuit the LM317 works for transmit radio waves in CW . The transmitter was done by SM0VPO and works very well , only not found the description the coil .  RF Transmitter using LM317 Circuit Diagram If you liked this article,Take a few Seconds to Share this and leave comments