Mechanical Relay Quality

[stj]

Re: Mechanical Relay Quality

that circuit is nice.
caps should be film type,
analog is not my thing, but the current drawn by the load is usefull to know.

you can get snubbers containing the cap and resistor in a single package but most designers use seperate parts.
probably for cost reasons.

[evilkitty]

Re: Mechanical Relay Quality

there should be no arcing, you need to add a snubber circuit across the contacts.

So i need to do this (see attachment)?
What kind of cap would i need to use here? This is an AC circuit (meter says ~26.995V)
about how many ohms should i use? (5, 10, 50, 100, 1000, 50k, 1m)
* my on hand resistors only good for 0.25W, so going below 3k is probably asking it to burn
AC caps are not polarized right?

In this case Load B would be used when the unit is set to heat and Load A would be used if the unit is set to cool


When i designed this board i used the relay to replace mercury tubes, i think i have seen a small spark when they switch, this is why i assume it was arc damage

[PopcornMobo]

Re: Mechanical Relay Quality

There's a good video showing what the cheap relays are capable of.
https://www.youtube.com/watch?v=ftJ17Cp6itw

[stj]

Re: Mechanical Relay Quality

there should be no arcing, you need to add a snubber circuit across the contacts.

[evilkitty]

Yesterday i had to replace a relay i installed about 2.5 years ago
This relay i used in my thermostat to use 5VDC logic to control 27VAC logic
I had used the cheap relays you can get on ebay for about $0.50 each (Songle SRD-05VDC-SL-C)
It failed cause the contact plate on the load side became dirty from electrical arcing
here is a video showing how they are designed: https://www.youtube.com/watch?v=KzR7EtPM15E

Would a 2.5 year life span be reasonable for a relay in this type of use? (defective?)
would one of these two last significantly longer (enough to justify 2 to 2.5 times the price)?
https://www.mouser.com/productdetail...wh-sh105d1f000
https://www.mouser.com/productdetail/JS1-5V-F