DIY Solid State Relay

Recently, solid-state relays have gained popularity. For very many devices of power electronics, solid-state relays have become simply necessary. Their advantage is a disproportionately larger number of operations, compared with electromagnetic relays and high switching speeds. With the ability to connect the load at the time of voltage transition through zero, thereby avoiding heavy inrush currents. In some cases, their tightness also plays a positive role, but at the same time depriving the owner of such a relay of the advantage in the possibility of repairing with the replacement of some parts. Solid state relay, in case of failure, is not repaired and must be replaced entirely, it is its negative quality. Prices for such relays bite a little, and it turns out wasteful. Let's try together to make a solid-state relay with our own hands while preserving all the positive qualities, but without filling the circuit with resin or sealant to be able to repair,in case of failure.
Do-it-yourself solid-state relay


Let's see the diagram of this very useful and necessary device.
Do-It-Yourself Solid-State Relay
The basis of the circuit is the power triac T1 - BT138-800 at 16 Amp and the optocoupler MOS3063 that controls it. On the diagram black wires are marked, which need to be laid with copper wire of increased cross-section, depending on the planned load. It is more convenient for me to power the LED of the optocoupler from 220 Volts, and it is possible from 12 or 5 Volts to anyone as needed. Solid-state relay with your own hands
To control from 5 Volts, you need to change the resistor 630 Ohm to change to 360 Ohm, the rest is the same. The parts are rated for MOS3063 if you use another optocoupler, then the values ​​need to be recalculated. Varistor R7 protects the circuit from voltage surges. The indicator LED chain can be completely removed, but it is clearer with it that the device works. Resistors R4, R5 and capacitors C3, C4 serve to prevent the failure of the triac,their ratings are calculated on a current not higher than 10 Amperes. If you need a relay for a large load, then the ratings must be recalculated. The radiator cooling for the triac directly depends on the load on it. With a power of three hundred watts, the radiator is not needed at all, and accordingly - the greater the load, the greater the area of ​​the radiator. The smaller the triac will overheat, the longer it will work and therefore even the cooler will not be superfluous. If you plan to control the increased power, the best output will be a triac of a higher power, for example, BTA41, which is rated at 40 amperes, or similar to it . The nominal parts are suitable without recounting.

Details and case

Solid-state relay by one's own handsDo-it-yourself solid-state relayWe need:
  • F1 - 100 mA fuse.
  • S1 - any low-power switch.
  • C1 - a capacitor 0.063 microfarad 630 Volts.
  • C2 - 10 - 100 microfarads 25 Volts.
  • C3 - 2.7 nF 50 Volts.
  • C4 - 0.047 μF 630 Volts.
  • R1 - 470 kΩ 0.25 Watt.
  • R2 - 100 Ohm 0.25 Watt.
  • R3 - 330 Ohm 0.5 Watt.
  • R4 - 470 Ohm 2 Watt.
  • R5 - 47 Ohms 5 watts.
  • R6 - 470 kΩ 0.25 watts.
  • R7 is a varistor TVR12471, or the like. br>
  • R8 - load.
  • D1 - any diode bridge with a voltage of at least 600 volts,or collect of four separate diodes, for example - 1N4007.
  • D2 - 6.2 Volt stabilizer.
  • D3 - diode 1N4007.
  • T1 - Triac VT138-800.
  • LED1 is any signal LED.

Making a Solid State Relay

First we plan the placement of a radiator, breadboard and other details in the case and fix them in place.
Solid-state relay by one's own hands
Solid-state relay by one's own handsDo-it-yourself solid-state relay The triac needs to be isolated from the cooling radiator with a special heat-conducting plate using heat-conducting paste. The paste should get out slightly from under the triac when the fixing screw is screwed.

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