Audible relay clicking sound

The relay should be mounted close to the object being powered but then 3 amps? You don't even NEED a relay most switches, especially automotive will handle that.

howie ll wrote: The relay should be mounted close to the object being powered but then 3 amps? You don't even NEED a relay most switches, especially automotive will handle that.

Funny you say that because I realized that later on after I finished the install. The switch I used to trigger the relay was rated for 10A at 125V AC --> http://amzn.to/2aL2kd9 Can you elaborate on the reason behind the "mounting close to the object" concept? Just wondering. Also, if a switch is rated for 10A at 125V AC, what would you guess it can handle up too in a 12V application? The description in the link I provided doesn't speak of 12V DC amperage.

I agree with howie ll that you didn't need the relay for a 3amp draw. Typically DC ratings are lower than AC due to the fact that AC is figuratively speaking only half on. AC voltage is reversing polarity from + to - and - to + at 60Hz (60 times a second). DC is always + or - on any given circuit when on. If it was rated for DC they would have probably given it a 10amps DC rating. 9amps would likely be the Max that I would use it for, and 6amps for continual use. I figure about half the rated AC for DC use to play it safe. Here is a better definition of SSR Relays: 3. Solid State Relays (SSR) SSRs are constructed using a photo-sensitive MOSFET device with an LED to actuate the device. See Figure 3. Solid State Relay (SSR): Light from the encapsulated LED actuates the photo-sensitive MOSFET and allows current to flow through it. SSRs are a faster alternative to electromechanical relays because their switching time is dependent on the time required to power the LED on and off - approximately 1 ms and 0.5 ms respectively. Because there are no mechanical parts, their life expectancy is higher than an electromechanical or reed relay. SSRs are useful for high-voltage applications because the LED actuation does provide a galvanic isolation barrier between the control circuitry and the MOSFET. Because the MOSFET is doing the switching, however, there is no galvanic barrier between its contacts. When there is no gate drive on the MOSFET, the drain-source channel on the MOSFET has a very high resistance providing the disconnection between the contacts. Because the connection is made via a transistor instead of physical metal like in electromechanical and reed relays, the contact resistance for an SSR is greater. Although technology improvements are continually improving the contact resistance of SSRs, it is still not uncommon to find them in production today with resistances of 100 Ohms or more. SSRs are not as robust as electromechanical relays. Much like reed relays, they are highly susceptible to surge currents and damage when used at signal levels above their rating. Although there are no metal contacts to weld, damage to the MOSFET can render the relay unusable.SSRs are common on matrices and multiplexers. Info about relay types found here: http://www.ni.com/white-paper/2774/en/

lurch228 wrote: I agree with howie ll that you didn't need the relay for a 3amp draw. Typically DC ratings are lower than AC due to the fact that AC is figuratively speaking only half on. AC voltage is reversing polarity from + to - and - to + at 60Hz (60 times a second). DC is always + or - on any given circuit when on. If it was rated for DC they would have probably given it a 10amps DC rating. 9amps would likely be the Max that I would use it for, and 6amps for continual use. I figure about half the rated AC for DC use to play it safe. Here is a better definition of SSR Relays: 3. Solid State Relays (SSR)

Thnx for the clarification on the AC vs. DC differences. Another device was also being powered via the switch so 4A in total. But as I wasn't sure what DC amperage rating the switch could handle, used a relay to be safe. Hence forth I will use the 50-60% rule for using AC switches in 12V DC application... Good info on the SSR... Here is a comment I got from another forum regarding using AC vs. DC rated switches --> An AC signal can be a complicated beast, and the voltage and current do not necessarily need to be in phase with each other, resulting in a lower power overall. For a DC signal, the power is just P = I × V, but for an AC signal, the power is P = I(rms) × V(rms) × cos(φ), where φ is the phase difference between the voltage and current signals. i don't know a lot about how electrical components are commonly rated, but i suspect that the required current rating for a 12 VAC 100 W switch is very different from the required current rating for a 12 VDC 100 W switch.

But more relevant here is the fact that if you assume the same power draw, the current through a 110 VAC switch will be much, much lower than through a 12 VDC switch. So you could use a 100 W 12 VDC switch in place of a 100 W 110 VAC switch, but not vice versa. In other words, using 110 VAC switches in a 12 VDC circuit... is probably not wise.

I think you're right though - the current is the key here. Make sure you're current-safe, and everything should be fine. http://www.frihost.com/forums/vt-102363.html

You basically got the point down. Inherent in any switch design to achieve a given rating is the the contact materials, the isolation factor, insulation, and overall resistance across the switch factors into it's ability resist fusing and heat it can dissipate. DC has inrush and wants to keep flowing as it never goes to zero. Ac starts at zero goes to positive threshold then back to zero then goes inverse to the same threshold and then back to zero again. This is 1 cycle and it does this at 60Hz(60 times per second) in the US.

Think of a relay in this case as a load switch, in other words you can user a cheaper lower rated switch and cheaper thinner rated wiring to the relay which is ideally located and fused between battery (source) and load this will of course increase the switch's longevity. Why do you think most vehicles have relays in underhood locations such as starter, fans, headlights etc.? I assume the OP isn't a pro as I've noticed similar very basic questions in previous posts, really Prince you should read up more before posting.

lurch228 wrote: You basically got the point down. Inherent in any switch design to achieve a given rating is the the contact materials, the isolation factor, insulation, and overall resistance across the switch factors into it's ability resist fusing and heat it can dissipate. DC has inrush and wants to keep flowing as it never goes to zero. Ac starts at zero goes to positive threshold then back to zero then goes inverse to the same threshold and then back to zero again. This is 1 cycle and it does this at 60Hz(60 times per second) in the US.

Got it thnx. I appreciate your explanations. I learn more everyday.

howie ll wrote: Think of a relay in this case as a load switch, in other words you can user a cheaper lower rated switch and cheaper thinner rated wiring to the relay which is ideally located and fused between battery (source) and load this will of course increase the switch's longevity. Why do you think most vehicles have relays in underhood locations such as starter, fans, headlights etc.? I assume the OP isn't a pro as I've noticed similar very basic questions in previous posts, really Prince you should read up more before posting

The point about the relays being under the hood doesn't apply to my setup because those devices you named are in close proximity to the power source -- the car battery in this case. I obtained my constant source from the ignition switch beneath the steering wheel column and had a SPDT switch triggering the relay mounted on the dash. So it made sense to me to mount the relay in close proximity to those items. Also, I have seen several installers on YouT mount relays beneath the dash when using them in alarm installs... Lastly, I have never claimed to be a pro or an expert like yourself but IMO have personally come a long way for someone who only began installing remote starters and things of the like a few months ago as a part time business and have learned a lot thus far. You don't see me asking what a transponder bypass is or the role of a GWR output or Tach wire when installing alarms or how to wire a relay to trigger Aux lights simultaneously from the OEM reverse light and manually from a switch do you? I assume you would consider those basic knowledge for your level of expertise right? I already installed the Aux lights for the client and used a relay to wire them to come one with the reverse lights and from a switch. I simply came on this forum to further expand on what I experienced (in this case, the clicking noise I hadn't noticed before when installing relays in previous applications). So your condescending tone isn't warranted. If my dumb questions are too ignorant and basic for your great highness, feel free to put me on your ignore list.

I was fishing for a reply! I thought you'd realise that the low current draw didn't need a relay. Fair enough I'll try and help you in future. And there's a way to stop the clicking, diode across 85 and 86, 1N4004 diode, band to the coil POS side.

howie ll wrote: I was fishing for a reply! I thought you'd realise that the low current draw didn't need a relay. Fair enough I'll try and help you in future. And there's a way to stop the clicking, diode across 85 and 86, 1N4004 diode, band to the coil POS side.

Finishing for a reply huh...Ok. Yea I understand the current draw was low but as the switch I had was rated for an AC circuit and didn't explicitly state what it could handle in a 12V DC setup, I wanted to be safe. So a simple 1A diode across 85 & 86 will stop the clicking sound from the coil energizing? Will try that next time. Thought the diode was only needed to absorb the high voltage spikes... Do you always use a diode with your relays?

Yup 1A diode that will work too. howie ll trumped me with the KISS method. Way to go howie ll