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Forum Index : Electronics : decade counter
| Author | Message | ||||
| irishron40 Senior Member  Joined: 22/09/2014 Location: IrelandPosts: 251 |
hi Like to know can a 4017ic switch a bt136 triac directly I do believe a triac can be swithed from abot 3 volt i like to use it as a relay to switch 220 volt . the load is only a few milli amp thx ron |
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| oh3gdo Regular Member  Joined: 18/11/2021 Location: FinlandPosts: 47 |
Irishron40 No, CD74HC17 can only drive 25mA and BT136 Triac needs 35 mA gate current. Can you use a normal transistor ex. PNP BC857 and it needs also a gate power supply like 0.5uF 400V with 100 ohm resistor in series with capacitor from 230V AC to 3.3V zener using a diode and a diode from a ground to capacitor. Plus a diode from capacitor to zener and 220uF 15V electrolytic capacitor. The transistor needs a limiting resistor limiting current like 100 ohms. The capacitor gives a enough current to gate, but takes only a little power. You van also use a switching external power source to gate current. Regards Pekka Ritmaki |
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| oh3gdo Regular Member Joined: 18/11/2021 Location: FinlandPosts: 47 |
Ia add a schematic for my triac connection triac.pdf |
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| irishron40 Senior Member Joined: 22/09/2014 Location: IrelandPosts: 251 |
ok thank you. I have some bc547 transistors which should be ok . thank you ron |
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phil99 Guru  Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
Potentially lethal unless an opto-isolator is added between input and transistor base. |
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