Relays for SFX

[SanTai]

I started thinking about relays and wanted to get some opinions

Most of the system that I use only use contact switches and there are no relays involved. I have not opened the hood on our gear that use relays too check what kind of relays they use.

The questions is: What kind of relay should you use in the live industry for SFX?

Only solid state or is the old mechanical kind with a coil good enough to use?
I am now thinking for applications such as kabuki drops, konfetti drops or other specials. Stuff that are not dangerous but are not allowed to go off prematurely. Could the bass from example a concert vibrate a mechanical relay to trigger? Or the sound effect from a thunder clap?

What do you use? Have you had any problem with the mechanical/coil relays? What is used in relay packs for lights?

 

[tdrga]

SanTai-

Mechanical relays are best if you need absolute on/off as SSRs can have a leakage current even when "off". I would never use an SSR (or dimmer) to trigger pyro, for example.
A good mechanical relay would be my choice 99% of the time.

-Todd

 

[SanTai]

SanTai-
...
to trigger pyro, for example.
...
-Todd

Thanks for the answer, but
I am specifically asking about non dangerous equipment, NOT pyro.

Though one application might be triggering a fan that spreads confetti from a pyro controller(They usually use 12-48 VDC, useless for a AC fan for example).
Is there no risk that the vibration from bass heavy music would trigger a mechanical relay?

 

[Les]

I think he was just giving an example of what he wouldn't use an SSR for and why.

I don't think you'd have a problem with bass triggering a relay. If that were the case, my relay pack would trigger lights when bumped, which they don't. I've also never heard any complaints from DJs concerning relays being too close to subs, so I believe you'd be fine.

 

[MPowers]

Part of your decision about which relays to use depends on the manner of their use. Will this be for a one off SFX that is used 3 or 4 weeks and then scrapped? Will it be for a theme park event that does 5 shows a day, every day year in, year out?

For example, The speed of the connection, the number of operations you need to happen before the relay fails, time delay between operations, reliability against false triggers.

Electronic relays react faster and can often perform several triggers in the same amount of time a mechanical relay can switch once. Electronic relays can perform many more cycles than a mechanical relay and the action and timing are virtually the same on the first operation and the last. Electronic relays are physically robust but tend to be susceptible to voltage fluctuations and spikes.

Mechanical relays are very robust, electrically and can usually handle a wide range of input voltage and frequency, but because the contacts and actions are physical parts that move, physical shock load conditions can damage them. Because the contacts and actions are physical parts that move, they wear out and the speed and firmness of connection may vary widely over time. Many mechanical relay make an audible noise when activated.

Mechanical relays are simply "Bigger", so if the size of your device is an issue, they may be a poor choice.

Anyway, hope this give you some things to think about.