About a year ago I got the idea to assemble a 12-220 volt voltage converter. A transformer was needed for implementation. The search led to the garage, where the Solntsev amplifier, which I had assembled about 20 years ago, was found. Simply removing the transformer and thus destroying the amplifier did not raise the hand. The idea was born to revive him. In the process of revitalizing the amplifier, many things have changed. Including power output indicator. The circuit of the previous indicator was cumbersome, assembled on K155LA3, etc. Even the Internet didn’t help find her. But another very simple, but no less effective output power indicator circuit was found.
This scheme is quite well described on the Internet. Here I will only briefly tell (retell) about her work. The output power indicator is assembled on the LM3915 chip. Ten LEDs are connected to the powerful outputs of the microcircuit comparators. The output current of the comparators is stabilized, so there is no need for quenching resistors. The supply voltage of the microcircuit can be within 6...20 V. The indicator responds to instantaneous audio voltage values. The microcircuit's divider is designed so that each subsequent LED turns on when the input signal voltage increases v2 times (by 3 dB), which is convenient for controlling the power of the UMZCH.
The signal is taken directly from the load - the UMZCH speaker system - through the R*/10k divider. The range of powers indicated in the diagram 0.2-0.4-0.8-1.6-3-6-12-25-50-100 W corresponds to reality if the resistor resistance R* = 5.6 kOhm for Rн = 2 Ohm, R*= 10 kOhm for Rn=4 Ohm, R*= 18 kOhm for Rn=8 Ohm and R*=30 kOhm for Rn=16 Ohm. LM3915 makes it possible to easily change display modes. It is enough just to apply voltage to pin 9 of the LM3915 IC, and it will switch from one indication mode to another. Contacts 1 and 2 are used for this. If you connect them, the IC will switch to the “Luminous Column” indication mode; if left free, it will go to “Running Dot”. If the indicator will be used with a UMZCH with a different maximum output power, then you only need to select the resistance of the resistor R* so that the LED connected to pin 10 of the IC lights up at the maximum power of the UMZCh.
As you can see, the circuit is simple and does not require complex setup. Due to the wide range of supply voltages, for its operation I used one arm of a pulsed bipolar power supply UMZCH +15 volts. At the signal input, instead of selecting individual resistors, R* installed a variable resistance with a nominal value of 20 kOhm, which made the indicator universal for acoustics of different impedances.
To change the display modes, I provided for installing a jumper or a latching button. In the final I closed it with a jumper.
Looking for a light switch or socket in the dark is not a pleasant experience. It’s much more pleasant when you see a glowing indicator in the dark and focus on it. It is especially useful to equip with such an indicator those sockets from which devices that do not have power indicators and fuses are powered. I offer an improved version of the device, equipped with a fuse blown indicator.
When there is no contact between the plug of the connected load and the socket, the indicator does not light, indicating that there is no “power take-off” from the load. When the load is "taking power" the blue LED will illuminate and when the load is drawing excessive power the fuse will blow and the red LED will flash.
The load connection indicator (LOI) consists of (Fig. 1):
When fuse FU1 blows, if the load is connected to socket XS1, current flows through the blown indicator elements that were previously shunted by the zero resistance of the fuse. Rectifier diode VD1 passes only negative
half-waves of the mains voltage, which flow through the current-limiting resistor R1 to the storage capacitor C1 and the load connected in parallel to it - the flashing LED HL1. VD1 protects HL1 from reverse voltage, and the zener diode VD2 protects HL1 from direct current overload.
When no load is connected to the XS1 socket, no current flows through the diodes VD4.VD6, the storage capacitor C2 is discharged and the field-effect transistor VT1 is closed.
The channel resistance (source-drain) is very high, and the HL2 indicator does not light.
When a load is connected to socket XS1, the load current flows through the back-to-back diode VD6 and the chain of diodes VD4, VD5. Negative half-waves of the mains voltage from the lower network wire in the diagram pass through VD6, and positive half-waves through VD4 and VD5.
The forward voltage drop across diodes VD4 and VD5 through resistor R2 and diode VD7 is supplied to C2 and charges it to a value exceeding the cutoff voltage (+0.6 V) of field-effect transistor VT1. Transistor VT1 opens and current flows through its channel, VD8, HL2, R4 connected in parallel, and then current flows through R3 and VD3. The HL2 LED lights up brightly, indicating that the load is connected. Resistor R3 is current-limiting, diode VD3 prohibits the flow of current during reverse half-cycles of the mains voltage. Resistor R4 eliminates the backlight of HL2 when VT1 is closed and, if necessary, is selected in the range from 3 to 8.2 kOhm.
The forward voltage drop across the current sensor (VD4, VD5) depends on the power of the connected load. In order for the indicator to “react” even to low-power (less than 1 W) devices, a relatively scarce field-effect transistor is used in the circuit. KP504A. It has a maximum source-drain voltage of 240 V and allows switching current in the drain circuit up to 0.25 A. The control voltage at the gate relative to the source is from 0 to 10 V. Cut-off voltage. KP504A is +0.6 V. The maximum load power connected to the XS1 socket is determined by the maximum forward current of the VD4.VD6 diodes (1.7 A) and should not exceed 500.700 W.
The circuit uses OMLT type resistors. Capacitor C1 is type K50-35 or foreign made with an operating voltage of at least 16 V, C2 is KM. Diodes VD1, VD3, VD8 - KD105B, KD102A or other miniature ones with a permissible reverse voltage of at least 200 V, VD4.VD6 - KD226V, KD226G, KD226D, VD7 - germanium. D2 or. D9 with any letter. Zener diode VD2 is low-power, with a stabilization voltage of 3.9...5.6 V, for example, KS139, KS147A, KS447A, KS156A. The HL1 LED can be replaced with a 5mm red MSD ARL-5013URC-B or a high-brightness non-blinking LED, for example, a yellow ARL-5213UYC. In the latter case, capacitor C1 can be eliminated. The HL2 LED can be replaced with any low-voltage green (ARL-5213PGC), white (ARL-3214UWC) or blue (ARL-3214UBC) color, preferably with increased brightness.
Almost all elements of the device are placed on a printed circuit board, the drawing of which is shown in Fig. 2. The board is built into a network outlet or into an adapter-splitter (“tee”), plugged directly into the outlet. It is possible to place it in the housing of the socket block at the end of the extension cord - “carrying”. Fuse FU1 for current. FOR - ceramic, miniature. It is installed in the head type fuse holder. DPB and placed on the front panel of the socket so that it does not interfere with the inclusion of plugs. When installing the indicator into a socket, the network wires that come to the socket contacts are carefully disconnected and connected to the board through terminal clamp blocks.
Looking for a light switch or socket in the dark is not a pleasant experience. Household light switches equipped with indicators that highlight their location have appeared on sale. By slightly improving the circuit, such an indicator can be turned into a load connection indicator.When a load is connected to socket XS1, the load current flows through the back-to-back diode VD1 and the chain of diodes VD2...VD6. Negative half-waves of the mains voltage pass through VD1. and positive ones - through VD2... .VD6. The voltage drop across the diodes VD2...VD6 is fed through resistor R1 to storage capacitor C1 and charges it to a value exceeding the cutoff voltage of field-effect transistor VT1. Transistor VT1 opens, and current flows through its source-drain channel, resistor R2, LED HL1 and diode VD9. The HL1 LED lights up brightly, indicating that the load is connected. Resistor R2 is current-limiting, diode VD9 prohibits the flow of current through the load during reverse half-cycles of the mains voltage. Diode VD10 protects HL1 from reverse voltage.
It should be noted that the forward voltage drop across diodes VD2.. VD6 depends on the power of the load connected to the XS1 socket and with a decrease in load power it also decreases. Therefore, in order for the indicator to “react” even to low-power (less than 1 W) loads, a KP504A field-effect transistor is used in the IPN circuit. It has a maximum source-drain voltage of 240 V and allows switching current in the drain circuit up to 0.25 A. The control voltage (0... 10 V) is applied to the gate relatively
source. The KP504A transistor has a cut-off voltage of +0.6 V. The maximum power of the connected load is determined by the maximum forward current of the diodes VD1...VD6 (1.7 A) and should not exceed 500...700 W.
The circuit uses OMLT type resistors. Capacitor C1 is oxide, type K50-35 or foreign made with an operating voltage of at least 16 V. Diodes VD1...VD6 are type KD226V. KD226G. KD226D. Diodes VD9, VD10 can be replaced with KD105B, KD102A or other miniature ones with a permissible reverse voltage of at least 200 V. Fuse FU1 is ceramic, miniature. It is installed in the head of the DPB type fuse holder and, together with the HL1 LED, is placed on the front (top) panel of the socket. If you have fuses soldered into the printed circuit board, you can do without a fuse holder. HL1 LED - almost any low-voltage LED with an operating current of up to 20 mA. To increase the brightness of the glow, it is recommended to use high-brightness LEDs as HL1, for example, ARL-5213PGC (green). ARL-3214UWC (white). ARL-3214UBC (blue). If with some types of LEDs, when VT1 is closed, a slight backlight of the LED is observed, the LED should be bypassed with a resistor with a resistance of 3...8.2 kOhm.
When installing the power supply in a socket, the aluminum network wires that fit the terminals of the socket are disconnected from them and connected to the input of the power supply through mounting adapters. All IPN components, except HL1 and FU1, are located on a board, the dimensions of which are determined by the internal dimensions of the socket.
A. OZNOBIKHIN, Irkutsk.
Often, when leaving home, you have to remember and then check whether any electrical appliances were left on. But some of them can not only “increase” the meter, but also cause a fire. The power consumption indicators described below will help eliminate this.
The basis of these indicators is a current transformer. A ring magnetic circuit with a winding is put on one of the network wires entering the apartment, forming current transformer. In it, the network wire acts as the primary winding of the transformer, and the winding on the magnetic core is the secondary winding. When any load is turned on, current flows through the power cable and an alternating voltage appears on the secondary winding, the value of which can be used to judge the electrical appliances that are currently turned on. The higher this voltage, the greater the power consumption.
In Fig. Figure 1 shows a diagram of a variant of a power consumption indicator with light signaling of the switched on load. The alternating voltage from the secondary winding is supplied to an amplifier assembled on element DD1.1, and from its output through capacitor C2 to a rectifier using diodes VD1, VD2. The rectified voltage is supplied to comparators on elements DD1.2—DD1.4; the outputs include LEDs HL1—HL3, signaling that electrical appliances are turned on.
If the total power consumption does not exceed 100 W, then the voltage at the inputs of the comparators corresponds to a low level, so none of the LEDs will light up. When the power consumption exceeds 100 W (but not more than 300 W), the voltage at the rectifier output will be sufficient to trigger only the first comparator on the DD1.2 element - the HL1 LED will light up.
If the power consumption is within the range of 300... 1000 W, then the comparator on element DD1.3 is triggered and the HL2 LED lights up, and the HL1 LED goes out, since in this case a low level voltage is supplied to the input of the element through the VD4 diode.
When the power consumption exceeds 1000 W, the comparator on the DD1.4 element is triggered, the HL3 LED lights up, and the HL2 LED goes out, since a low level voltage is supplied to the input of the DD1.3 element. Of course, you can choose other gradations of displayed power.
The design of the current transformer and its current-voltage characteristic are shown in Fig. 2. Its magnetic core is a 2000 NM ferrite ring of standard size K20X10X5, which is carefully broken into two parts and 1500 turns of PEV-2 0.08 wire are wound onto one of them - this is the secondary winding 3. Then, putting the second part of the ring 2 on the network wire 1, both halves are glued with BF-2 glue or epoxy glue.
Rice. 1. Diagram of a power consumption indicator with light signaling of three load levels.
Rice. 2. Design (a) and current-voltage characteristic (b) of the current transformer.
Rice. 3. Printed circuit board and layout of elements of the power consumption indicator with light signaling.
In this case, the magnetic properties of the ring, glued together without a gap, deteriorate slightly. The terminals of the transformer winding are connected by insulated wires to the circuit board of the device (Fig. 3), located in a housing of a suitable size. Power switch SA1 - can be located on the indicator body and turned on manually or installed on the door jamb so that power supply is supplied to the indicator when it is opened.
Set up the indicator in the following sequence. A load with a power of about 300 W is connected to the mains and by selecting resistor R1, LED HL2 lights up. Then connect a load with a power of 100 W and select resistor R7 to make LED HL1 glow, and when the load is reduced by 20...30 W, this LED should go out. After this, a load with a power of 1000 W is connected to the network and the tuning resistor R5 is used to make the HL3 LED glow.
It is best to place the current transformer in a distribution box, usually located in the hallway of the apartment.
The circuit and circuit board of another version of the power consumption indicator are shown in Fig. 4, a, b. This indicator has a sound alarm and, in addition, has a “memory”.
As in the previous design, the alternating voltage of the current transformer is rectified by diodes VD1, VD2, but unlike the previous version, capacitor C2 of a much larger capacity is installed in this one, in addition, the input resistance of the comparator and generator on elements DD1.1 is increased. DD1.2, which is used to save information about the value of power consumption for several minutes.
This is necessary in cases where the load is not constantly connected to the network (for example, an iron with a thermostat). If the power exceeds a preset threshold, then the generator starts working on elements DD1.1 and DD1.2 and a sound signal is heard in the phone with a frequency of about 1 kHz. This device, whose sensitivity is relatively low, should be used to indicate power consumption of 1000 W or more.
Rice. 4. Scheme (a) and circuit board (b) of a power consumption indicator with an audible alarm.
The current transformer is of a similar design; see its description in the first version. The setup comes down to selecting resistor R1 to indicate the inclusion of a load of a certain power. The BF1 phone must be high-impedance.
Literature: I. A. Nechaev, Mass Radio Library (MRB), Issue 1172, 1992.
Schematic diagrams of simple indicators of the presence of a 220V network on LEDs, we replace old neon indicator lamps with LEDs. In electrical equipment, neon indicator lamps are widely used to indicate that the equipment is turned on.
In most cases, the circuit is as in Figure 1. That is, a neon lamp is connected to an alternating current network through a resistor with a resistance of 150-200 kioles. The breakdown threshold of a neon lamp is below 220V, so it easily breaks through and glows. And the resistor limits the current through it so that it does not explode from excess current.
There are also neon lamps with built-in current-limiting resistors; in such circuits, it seems as if the neon lamp is connected to the network without a resistor. In fact, the resistor is hidden in its base or in its lead wire.
The disadvantage of neon indicator lamps is their weak glow and only pink color, and the fact that they are glass. Plus, neon lamps are now less common on sale than LEDs. It is clear that there is a temptation to make a similar power indicator, but on an LED, especially since LEDs come in different colors and are much brighter than “neons”, and there is no glass.
But, LED is a low-voltage device. The forward voltage is usually no more than 3V, and the reverse voltage is also very low. Even if you replace a neon lamp with an LED, it will fail due to the excess reverse voltage at the negative half-wave of the mains voltage.
Rice. 1. Typical diagram for connecting a neon lamp to a 220V network.
However, there are two-color two-terminal LEDs. The housing of such an LED contains two multi-colored LEDs connected back-to-back in parallel. Such an LED can be connected in almost the same way as a neon lamp (Fig. 2), only take a resistor with a lower resistance, because for good brightness more current must flow through the LED than through a neon lamp.
Rice. 2. Diagram of a 220V network indicator on a two-color LED.
In this circuit, one half of the two-color LED HL1 operates on one half-wave, and the other half on the other half-wave of the mains voltage. As a result, the reverse voltage on the LED does not exceed the forward voltage. The only drawback is the color. He is yellow. Because there are usually two colors - red and green, but they burn almost simultaneously, so it visually looks like yellow.
Rice. 3. Diagram of a 220V network indicator using a two-color LED and a capacitor.
Figures 4 and 5 show a circuit of a power-on indicator on two LEDs connected back-to-back. This is almost the same as in Fig. 3 and 4, but the LEDs are separate for each half-cycle of the mains voltage. LEDs can be either the same color or different.
Rice. 4. 220V network indicator circuit with two LEDs.
Rice. 5. Diagram of a 220V network indicator with two LEDs and a capacitor.
But, if you only need one LED, the second one can be replaced with a regular diode, for example, 1N4148 (Fig. 6 and 7). And there is nothing wrong with the fact that this LED is not designed for mains voltage. Because the reverse voltage across it will not exceed the forward voltage of the LED.
Rice. 6. 220V network indicator circuit with LED and diode.
Rice. 2. Diagram of a 220V network indicator with one LED and a capacitor.
In the circuits, two-color LEDs of the L-53SRGW type and single-color LEDs of the AL307 type were tested. Of course, you can use any other similar indicator LEDs. Resistors and capacitors can also be of other sizes - it all depends on how much current needs to be passed through the LED.
Andronov V. RK-2017-02.
