What's this about

This circuit implements a simple, yet versatile, on-delay time relay based upon the 555 timer. It was designed for simplicity, so all components are through-hole and you can choose the values for the RC net that sets the maximum delay. Even more, you can also use any relay coil from 5VDC to 15VDC.

An On-delay time relay is a relay that closes its contacts (C-NO) after a period of time has ellapsep since it receives power.

Unlike cheap on-delay time relays out there, this design includes an internal router slot for helping in to avoid electric arcs and carbonisation. Even more, high power tracks are exposed so you can apply extra tin (or even a piece of wire) to help carry high currents.

Last, but not less important: it looks great! You can choose any silkscreen color you want. And it's only 71mm x 22mm.

Bill of materials (BOM)

Despite I needed to upload a BOM, what makes this project awesome is that you can choose most of their components/values:

• RV1 is a 3362 miniature single turn potentiometer and you can choose its value (along with C1) to set up the maximum delay. You can also used a 3296 multi-turn pot (not recommended) or a bigger one single turn pot: 3386 (in this case delay direction setup is flipped, be aware).
• The value for C1 can be chosen up to 1000uF. The PCB is ready to accept it in the 25V or 50V version.
• You can even choose the coil voltage for the relay, from 5VDC to 15VDC, and from 10A to 15A. How cool is that?

In order for this project to perform as it was designed, please use 555 original chips from well known manufacturers: TI, ST or ONSEMI. Don't accept fake copies of it! Preferable that you gather them from an also well known distributors: mouser.com, digi-key.com, etc.

You can read about this project and get its schematic here (currently in spanish, but soon will be available in english too).

IMPORTANT: Before you place your order, make sure to select the solder mask/silkscreen colors that you like the most and the quantity you need. If you aren't in a hurry, you can choose an economic courier that will last a little longer, but with an affordable cost.