Hoffman Amplifiers Tube Amplifier Forum

Other Stuff => Solid State => Topic started by: offabit2001 on November 20, 2019, 01:48:12 pm

Title: RELAYS FOR DUMMIES (OR JUST ONE DUMMY, ME)
Post by: offabit2001 on November 20, 2019, 01:48:12 pm

O.k. guys, you"ve all been a wealth of knowledge so let me pick your brains. This will probably be a multiple part discussion. I want to kind of make a thread for dummies about relay switching for myself and others who are new to using them. Believe me when I say I have gone over the main relay discussion pages a few times. Some of it I get, other parts are Greek to me. Im going to start off simple.
Question 1:
Using the logic in the below picture A, would it not be true that picture B seems to be logical. If not, please tell me what I'm missing and why. Lets say I'm making a simple signal slitting pedal. Channel 1 goes to amp 1 and channel 2 goes to amp 2. In my mind, when the relay in NOT energized, the signal in channel 1 would be open while channel 2 would be grounded. Once energized, channel 2 would be open and channel 1 would be grounded. Is this right? Hold on everybody this is going to be a bumpy ride. :w2:

Title: Re: RELAYS FOR DUMMIES (OR JUST ONE DUMMY, ME)
Post by: sluckey on November 20, 2019, 02:06:30 pm

This is the only pic you need to look at to be able to wire up that relay properly...

(http://el34world.com/projects/images/Img_7147.jpg)

Title: Re: RELAYS FOR DUMMIES (OR JUST ONE DUMMY, ME)
Post by: pompeiisneaks on November 20, 2019, 06:22:23 pm

I would add to this that this diagram is excellent, and on top of it, relays are wired differently that most switches.  Most switches have COM in the center and NO or NC on the outer sides, but relays have COM as the (4/13) pins which are the first/last depending on your point of view in the switch.  I messed this up the first time I wired one up... :)

~Phil

Title: Re: RELAYS FOR DUMMIES (OR JUST ONE DUMMY, ME)
Post by: PRR on November 21, 2019, 02:05:19 pm

> relays are wired differently that most switches.

The makers keep it internally simple. Here is what is inside a typical small relay:

(https://pi-plates.com/wp-content/uploads/2015/11/NC-RELAY.jpg)

The NC/NO contacts are close together. The COM is a long lever so the connection is a bit further away.

This particular relay has the coil in the middle. Most micro relays have the coil sideways at the end, working an arm on the armature hinge, so the coil terminals are all the way left (in this view).

But there are many variations. I have a blower relay with places for 47 terminals. While mine only uses 8, I absolutely needed the maker cheat-sheet to figure it out.

Title: Re: RELAYS FOR DUMMIES (OR JUST ONE DUMMY, ME)
Post by: pompeiisneaks on November 21, 2019, 04:15:41 pm

makes perfect sense. 

thanks for the detail PRR.

Pictures, 1000 words... etc :)

~Phil