Why switches and relays can't handle much DC current?

You may noticed that switches and relays are rated to handle a small DC current compared to the AC rating. Here is why

[@SciPunk215]

7000 subscribers, and fully 2/3 of them got excited by the rapid switch clicking. Keep doing what you do, John.

[@KevinDay]

I knew the answer, but I wasn't aware of those Omron relays. Thanks for the info.

[@edibleacres]

Wondering if you may have a suggestion for me... I have a load port from a solar charge controller that when turned on produces 58.2V but only 1A or so. Strange combo. I am hoping to figure out a simple relay that can take a control DC voltage of 58.2 (or higher since that is an odd number) and be able to safely and reliably control the on/off of the load. It would be controlling the positive run of a series string of 3 solar panels that produce I believe roughly 80V at 5 or 6A... Thanks so much for any leads!

[@H2ON_MEA]

Thanks

[@rustyshackleford9066]

So glad I found your channel. This was informative. I'm playing with DC motors, 90 - 130 volt range with current anywhere from low single digits up to almost 30amps. Using line voltage through an AC inductor/choke/coil to an SCR to adjust voltage, fused, passing through a diode bridge rectifier and DC large block choke. I'd like to be able to switch the motor direction after the power is converted to DC. I've seen lots of guys using DPDT 12VDC 30 amp toggle switches like the 28E-MTD. Watching his video, it makes me question if doing so is a good idea. Is that risky? Any suggestions on DPDT switches I could use with those VDC and current levels? Also, does it even make sense to do so or would it damage the motor? I don't expect to switch at high speed but it would be nice to know the switch can handle it it I mong it up. Thank you.

[@JohnAudioTech]

I would go to a trusted supplier such as DigiKey or Mouser and check their products. The data sheets for the switches should provide the safe DC voltage and current ratings.

[@on1ytheb3st]

What about using a switch in an application with a lower voltage than its maximum parameter, will that allow a higher maximum current than its rating? For example, a switch with a rating of 30V DC and 0.3A, could it be used in an application with a 1S lipo battery where the supplied voltage would not exceed 4.2V but the current could increase to 2A?

[@joohop]

Can You Do A Vid On SCR 's Please Bud ? ATB ;)

[@aztec1077]

ok i get the theory but now im confused ......here is what i want to do i just want to power on and off an led strip at 5v 2 amps max DC ( usb power brick) so i cant use a latching switch that i find on amazon? ive seen switches but they only give AC specs 125V 5A....only managed to find a 30V 1A DC switch but i need just need 5V 2A. BUT here is my confusion how is it that ive seen power on/off switches built in the usb cable thats rated for 5V 2A DC? (for example power on/off usb cable used for a raspberry pi ) OR powered usb 3.0 hubs with a 5V 3A DC power supply that have power on/off switches ????? what switches are they using? are they using some other logic with it? and where can i find it?

[@tl2797]

Thank you for this explanation! Can I ask what camera are you using?

[@JohnAudioTech]

I use a Canon ELPH 115 IS.

[@tl2797]

Thank you very much! I'm thinking of getting a camera so I need a reference point :)

[@FuttBucker42069]

That voice crack 😂😂☠️

[@josephn2xbn321]

I use to increase the dc current of a switch by placing a cap in parallel of the switch, the ark bypasses the switch then.

[@rustyshackleford9066]

Smart. Seems like a challenge finding DPDT switching for 90 - 130VDC at almost 30amps. I'm monkeying with motors and want my DC motor direction switching to be safe.

[@afrog2666]

Are there any inexpensive simple switches suitable for 5V, 25A? More specifically, up to 4.2V, at a maximum of 25A but more like 20, In burst up to 5 seconds.. Loads from 1ohm to 0.2ohm.. I`m a vaper, looking to build a mod, and I would like to do it without using a MOSFET. Just an 18650 cell in a very simple circuit with a switch going to a 510 connection. But I can`t seem to find switches rated higher than 5A :/ One thought was simply using a spring loaded copper rod, but I`d have to completely change my design as well as making a safe and reliable switch assembly myself :/

[@JohnAudioTech]

I'd look on Mouser or Digikey. Their filter tool can be useful in finding items like that. I'd imagine a 25A switch will probably be fairly large. I'd still lean towards a MOSFET. Look for a high current one with very low Rds on and gate voltage. Problem there is driving the gate with enough voltage to turn the MOSFET on hard enough for the heavy current. You can parallel them too.

[@afrog2666]

Will do, thanks! :)

[@Mr_Meowingtons]

i ran an old cairn at the steel plant in 2003~2007 it was a 220V DC cairn made in 1930's it was old school as F#@& any way it had a Knife Switch to power it up and down and if you opened the Knife Switch slow you can get that ark to go 2"

[@tdevosodense]

? What about relays in cars ? Thats 30amp/12volts

[@JohnAudioTech]

Switching 12 volts is not really a problem.

[@edslh9867]

hi john, pm mail pls~ I got noise issue and hope to have ur advice. tq