T2850D RCA Triac 400V 8A RMS TO-220 AC Thyristor Switch, Unused NOS

RCA T2850D 400 V 8 A Triac for AC Phase Control and Load Switching, TO-220 Body

Condition

Unused new old stock (NOS). Markings legible: T2850D RCA. Sold each.

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Product Overview

A 400 V, 8 A RMS triac from RCA in a three-lead TO-220 body, part number T2850D. A triac is a bidirectional thyristor: a gate pulse turns it on in either direction of the AC cycle, and it stays on until the load current falls toward zero at the end of the half cycle.

Key Features

• Device type: triac (bidirectional AC thyristor)
• Repetitive peak off-state voltage (VDRM): 400 V
• RMS on-state current IT(RMS): 8 A
• Package: TO-220, three through-hole leads, metal mounting tab with hole
• Terminals: main terminal 1, main terminal 2 and gate

Applications

• Replacing the power triac in a lamp dimmer, fan speed control or appliance control board
• Phase-angle speed control of universal motors in tools and small machines
• Switching heaters, lamps and solenoids on line-voltage AC from a logic signal through an optotriac driver
• Building a discrete solid-state relay on the bench

Frequently Asked Questions

What does the D in T2850D mean?

In RCA's T28xx triac numbering the D suffix marks the 400 V grade. The T2850D is rated 400 V VDRM.

Does it conduct in both directions?

Yes. Once the gate triggers it, a triac conducts on either half of the AC cycle, so one part switches a full AC load.

How do I tell it apart from a transistor in the same TO-220 body?

By what the three leads are. A triac has two main terminals and a gate, and once triggered it conducts in either direction. A power transistor in a TO-220 body has base, collector and emitter instead.

Larger orders lower the price per piece; the price-break table on this page has the details.

The whole job of this RCA part is timing: wait out part of each half wave, then let a gate pulse switch it on, whichever way the current runs. Where in the sine wave you fire it is your call.