USB LED Night Light Circuit Diagram

A typical USB LED bulb shown in Fig. 1 is a 5V, 5W USB-powered solid-state lamp. At the heart of this light bulb is a circular aluminium PCB made with a bunch of 5730 SMD super-bright LEDs. Typical working voltage of a single 5730 SMD LED is in the range of 2.9V to 3.4V, and its current consumption is about 150mA. Fig. 2 shows some details of SMD LEDs used in the USB LED bulb. 

This gizmo inspired me to design a distinct USB LED night light with battery backup. Read More Click He

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Heater and Ventilation Control

This is a guest post by our visitor Etienne F. For any questions please contact the author (email address link is given below). This circuit control a heater and a fan at variable speed and intensity with over temp and under temp alarm. The control work with a thermistor for the temperature reading and the setpoint is variable. The speed and intensity work with a difference between the temperature reading and a setpoint. At all time, only one of the system works (heat or ventilation) or if the temperature is near the setpoint, none of them work.

1st block: temperature reading and setpoint voltage:

The reading of the temperature to generate voltage

Difference between set point and temeprature reading:

For the first PWM voltage value, the input from the LM324 subtract the temp reading and the setpoint. The result is multiply by the pot between the out and the + input of op amp U2b (ratio from the resistance and the pot.) (Value in ohms). The result is send to the – input of Op amp U2c and the second 100K pot is use to set the offset voltage (2Vdc in my circuit). The result is send to the input of the PWM control block. The correct ratio should be around 2 :1 (multiply by 2 the voltage) The 1N4007 Diode keep the voltage over 0V (the result of the subtractions can be negative but the PWM need a voltage between 0 and 12V DC)

The voltage for the LM324 is +12 and -12VDC (pin 4 and 11) The second block subtract the setpoint voltage to the temperature reading. The result is multiply by the pot. (Depending of the value of the potentiometer). The ratio between the 56K resistance and the value of the potentiometer define the multiply ratio. The output equation is Vin X (Pot /R1) = -Vout The next op amp input add a voltage value to the result (2V) and the last amp is used to reverse the result.

3rd block: voltage generator proportional to a high temperature (PWM)

The block consists of an LM324 (quad op amp) which is used as a comparator (compare the temperature reading at set point), a square wave generator whose frequency varies according to the set point and the temperature reading. This square wave into an oscillator circuit which, after being compared to the set point (which is a triangle wave that varies between 4V and 9V has a frequency of 45Hz). The triangular wave enters into a circuit to be compared to the value of reading. When the reading exceeds the value of the triangular wave form is a square wave and the output is 12V.

More reading approaches the set point, the longer the 12V signal is activate and when the reading exceeds the maximum of the triangular wave (9V), the fan runs at maximum speed. The square wave into a MOSFET to be amplify (the ratio of on / off is increased). The duration of the excess voltage determines the duration of 12 V. The 0.1uF capacitor (C3) between the + and – of the load makes the signal clearer.

High and Low Temp Alarm:

 

Part list :

U1, U2, U3, U4, U5 : LM324 quad amp
Q1 : IRF521 MOFFSET
Q2 : TIP31C
D1, D2, D3, D4 : 1N4007
C1 and C2 : 1uF capacitor
C3 and C4 : .1uF capacitor

47K thermistor
Resistance :
19X 56K
10X 100K
2X 3.3K

Author: Etienne F

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Kitchen Exhaustion Fan Controller

Exhaustion fan is a very important element in kitchens. Here may be a easy circuit to manage kitchen fans by monitoring the ambient temperature. it's engineered round the renowned precision integrated temperature sensor chip LM35 (IC1). remainder of the circuit may be a non-traditional electromagnetic relay driver wired round the fashionable LED driver LM3914 (IC2). User will switch 3 presetted temperature levels employing a jumper/slide switch (JP1), that determines the warmth level to activate the relay and hence the electrical exhaustion fan wired through the relay contacts. It works off 12V DC power offer.

Kitchen Exhaustion Fan Controller  Circuit Schematic

Only one adjustment is needed during this kitchen Exhaustion fan controller circuit. when construction, set jumper purpose in its 1st position, ie base terminal of T1 is connected to pin thirteen of IC2 and alter the preset P1 fastidiously in order that relay RL1 is energised when ambient temperature level reaches close to 29oC. but this is often not terribly vital as you'll choose any threshold level by connecting the jumper points to alternative unused output pins of IC2 (here solely three outputs are used).

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Numeric Water-Level Indicator

Most water-level indicators for water tanks are based upon the number of LEDs that glow to indicate the corresponding level of water in the container. Here we present a digital version of the water-level indicator. It uses a 7-segment display to show the water level in numeric form from'0' to '9.' The circuit works off 5V regulated power supply. It is built around priority encoder IC 74HC147 (IC1), BCD-to-7-segment decoder IC CD4511 (IC2), 7-segment display LTS543 (DIS1) and a few discrete components. Due to high input impedance, IC1 senses water in the container from its nine input terminals. The inputs are connected to +5V via 560-kilo-ohm resistors.

The ground terminal of the sensor must be kept at the bottom of the container (tank). IC 74HC147 has nine active-low inputs and converts the active input into active-low BCD output. The input L-9 has the highest priority. The outputs of IC1 (A, B, C and D) are fed to IC2 via transistors T1 through T4. This logic inverter is used to convert the active-low output of IC1 into active-high for IC2. The BCD code received by IC2 is shown on 7-segment display LTS543. Resistors R18 through R24 limit the current through the display.


When the tank is empty, all the inputs of IC1 remain high. As a result, its output also remains high, making all the inputs of IC2 low. Display LTS543 at this stage shows ' 0, ' which means the tank is empty. Similarly, when the water level reaches L-1 position, the display shows '1, 'and when the water level reaches L-8 position, the display shows '8.' Finally, when the tank is full, all the inputs of IC1 become low and its output goes low to make all the inputs of IC2 high. Display LTS543 now shows '9,' which means the tank is full. Assemble the circuit on a general-purpose PCB and enclose in a box. Mount 7-segment LTS543 on the front panel of the box. For sensors L-1 though L-9 and ground, use corrosion-free conductive-metal (stainless-steel) strips.

Copyright: EFY Mag

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