A power source for LDS
Device, scheme of which is given below, is used to gas leak detection.
The sensor detects methane, ethanol, hydrogen, isobutane. You can change this list by simply applying another sensor in scheme. Comrades from the office Figaro produce a bunch of different of sensors for detecting various gases.
Diagram of the device such (to get the bigger scheme, it is necessary to press on a little):
(click to enlarge)
Will go quickly in terms of functional groups scheme.
Thus, the sensor SE1 is a plate with some oxide, which is heated by an embedded heater.
In pure the air sensor resistance is approximately 10 ohms. When the appearance in the air of particles in the gas, the resistance of the sensor begins to fall - the stronger, the greater the gas concentration. When a certain threshold comparator on the chip DA2 changes its state, and starts working generator DD1.1. In this connection, blinking led HL2 and terrible beeping beeping buzzer SP.
Node DD1.3 provides a delay time of approximately 2 minutes. This is due to the fact that the sensor heater needs time for it to warm up and recover. Indicator HL3 just lights up after 2 minutes, and signaling of the sensor to work.
Eats the whole thing from a regulated source voltage 5 volts on the chip DA1.
The symbol on the schematic
R3, R13, R14
R4, R9, R11, R12
Bourgeois analogue 1N4148
Bourgeois analogue LM317
Bourgeois analogue LM358
Bourgeois analogue HCF4093
Depends on the type of gas.
Any voltage on the secondary winding 7-9 volts and a current of 300-400mA
Any with built-in generator
First of all, break the positive power supply pin diagram (somewhere in the region of the first led) and a configurable voltage regulator resistor R1. Set of 5 volts as accurately as possible. Then restore the schema and connected to the network. After about 2 minutes should light up led HL3. Again measure the voltage at the output stabilizer, and if necessary, adjust it. Measure the voltage at pin 2 of the chip of DA2 and the resistor R6 installed on a couple of tens of millivolts less measured at the output 3 of the same chip. Next, take the lighter (gas of course) and begin to put gas in the face of the sensor. Must light up the led HL2 and squeaked buzzer. The sensitivity is adjustable by the resistor R6.
This can be considered finished setting.
In conclusion I would like to note that to install the sensor in wet areas is not recommended because of its resistance depends on humidity. Therefore, do not install it directly over or near home a gas stove.
Publication: www.radiokot.ru, www.cxem.net