SOLVED Basic Relay Bypass

[Big Monk]

I wanted to incorporate relay switching into my Monk Face design.

I chose the Basic Relay Bypass schematic:



I incorporated it directly, making a few changes:



Q1 is a BC547A because that's what I had on hand. Used a 78L05 and adjusted the VRef divider resistors. Added a 100u cap after the regulator.

I soldered in just the components for the switching onto a Monk Face board to test the LED first.

Here is what I am getting:

All solder connections are good. Continuity where required. Voltages seem bang on. Here's what I'm using:

https://www.taydaelectronics.com/datasheets/A-176.pdf

Looks like the dropout voltage is 1.7v.

I'm only using the 4.5v Vref for the relay and it's associated circuitry, i.e. the NE555.

Just checked voltages:

Vref = 4.52v
Vcc = 8.33v

Reg3 = 5.04v
Reg2 = 0v
Reg1 = 8.33v

NE555:

Pin 2/6 = 4.52v
Pin 4/8 = 8.33v

Switch Pin 1 = 4.52v

BC547A (2N3904 sub) collector has continuity with LED -.

 

[szukalski]

Yup! That's what I did to verify operation and what I'll do on the 2 boards I saved for test units.

Also, thank you for the heads up on that other 8 Pin relay from Fujitsu. Not only is is smaller, but cheaper as well. Even accounting for shipping outside of the Chinese Mainland, they are $0.85 per unit and much less at volume.

Way cheaper right? They have two sizes which are identical (depends if you want height or width to be small).

I have a dual size footprint here for Diptrace, so you can use either on the same board:

sheepylove-diptrace/Sheepylove at main · szukalski/sheepylove-diptrace

Diptrace library for building PCBs. Contribute to szukalski/sheepylove-diptrace development by creating an account on GitHub.

github.com

 

[Big Monk]

Way cheaper right? They have two sizes which are identical (depends if you want height or width to be small).

I have a dual size footprint here for Diptrace, so you can use either on the same board:

sheepylove-diptrace/Sheepylove at main · szukalski/sheepylove-diptrace

Diptrace library for building PCBs. Contribute to szukalski/sheepylove-diptrace development by creating an account on GitHub.

github.com

Ordered new boards, new relays, and new ground springs. Fingers crossed....

I really like that LCSC is a single sign on with JLCPCB.