confused about power

I fear my ignorance is showing....

I am looking for some way to induce conductivity between two wires -- I thought these might do it, but they rely on sharing a ground with the wires being connected...

I have a device that exposes two leads, when they are connected with a mechanical switch then the device is actuated.

I want to connect those two leads using the pico, but I can't introduce any current into them.

I don't really want to use a mechanical relay for this (like the ones in the powerstrip) but I will if I have to.

A relay would do the job since it's powered totally independently from the wires being switched

I guess I'll go search for solid-state 3.3v controlled relays

I should have started a new thread for this question...

Something like this?

http://www.futurlec.com/Relays/JRC-23F-0­3.shtml

It is really dangerous for someone with such lack of knowledge in electrical safety to be messing around with mains voltage, especially if there are "signal" wires coming out of the contraption, and these wires are accessible so someone can touch them.
The type of relay boards (and relays) in the picture were never designed with electrical safety in mind and certainly would not pass mandatory electrical safety test requirements if they were part of a product that was marketed. That these relay boards can be bought on the internet is no guarantee that they are safe to use in mains voltage applications.

I'm not going to say 'It's fine' unless I get sued, but @user58511 seems to have been pretty careful.

Most electricians will have very little idea about actual electronics. It doesn't mean they're at risk of electrocuting themselves or those they work for though. Just because @user58511 is willing to ask for help about problems with electrical interference doesn't mean he doesn't know about electrical safety.

Also, those relay modules look pretty good to me. I've seen plenty of commercial stuff that has far less of a gap between high and low voltage than they do.

@user58511 I think the thing you posted is just another relay? If you look for 'solid state relay' in eBay you should see a bunch of things that will switch mains voltages... Internally, SSR modules use a Triac (which does have a physical connection to the wires it's switching), but the module contains other components including an opto-isolator, to ensure that the 2 wires going in are completely disconnected from those going out.

http://www.ebay.co.uk/itm/272159069775 uses an OMRON G3MB-202P looks like a good bet.

Having said that, SSRs only work for switching AC power (otherwise you can turn them on, but never off). If you wanted to switch DC in an isolated way, without using contacts, then I'm not sure you can buy a module - you might have to make something with an opto-isolator and FET.

Tage, thanks for your concern. But I think there may be some confusion. I am not trying blindly to substitute relays to get rid of the problems with the EMI. I'll be decoupling the 5v DC power to try to finish accomplishing that. That being said, if you think the sain-smart relays were a bad choice to drive little 1&2 amp loads, I'd sure like to know what I might replace them with.

You do raise an interesting point tho' as my contraption does have wires coming out of it that are not intended to carry mains voltage. Are you are saying that if there was some arcing situation within the powerstrip that mains current could exit it via the signal wires and be available for contact? In that case I think I'd be lucky in that the pico would die and the circuit would then be unable to be closed by contact, yes?

In any case, would it be sufficient to place GFCI protection between the mains and my contraption? something like this: http://www.petsolutions.com/C/Aquarium-P­ower-Strips-Timers/I/GFCI-Outlet-Adapter­s.aspx (just to pick one that I found in a few moments searching.)

Now these other relays are for a different project, and I should have started a different thread. This other project has absolutely nothing to do with the mains.

The smaller relays that I'm looking at are to achieve conductivity between two wires to replace mechanical switches that are used in a battery operated device that considers the closing of the contacts a reason to send a complicated signal via bluetooth to a computer.

Ahh, ok - so the relay you found would be pretty good for that (but you still need a nice way to drive it from Espruino), and SSRs wouldn't be useful.

For small battery powered devices, you might find a simple optocoupler works fine for you - like: http://uk.farnell.com/isocom/sfh615a-4x/­optocoupler-dip-4-tr-o-p/dp/1683350

It's rated at 50mA....

The only 'gotcha' there is as it's not a switch, you're going to have to make sure that you connect + and - on the device the right way around.

Here is a solid state relay that can switch DC:

http://www.dx.com/p/ssr-10dd-solid-state­-relay-white-silver-232097#.V1a2zm6eqrU

There are different models, with different amp loads and for ac or DC.

http://www.dx.com/s/solid+state+relay

What is the reason not to use a relays for making connection between two wires of which you do not know what the dynamics are? In the original setup, they require a galvanic connection and I would stick with it.

The question is also: is the original switch a momentary or and on-off switch? No matter what, you have power dependency...

If it is a normal on-off switch:

Case one: with a normal relays a power fail disconnects and you need a manual override (parallel on-off switch)

Case two: with a bistable relays, a power fail leaves you stuck with the last state and you need a manual override (in series with one of the on of a on-off-on switch, where the other on make the direct connection).

Ah, let's all come to the same page: http://www.pretorianuk.com/j-pad

I have one of these, and the person I'm doing this for can't operate the joystick, I chose the device also because it has the option to attach external switches.

I want to make touch-pads so that I can close those [external switch] circuits programmatically.

Gordon, those optocouplers are gorgeous -- I saw something like them in my searching last night but couldn't figure out if I could drive them from the pico as they didn't seem to mention Volts... Those mention 6v but in ways that I don't understand, and I don't know what your reference to 50mA means, the pico has 250mA to spread around so I'll have enough to drive these? Or I'll fry them unless I add a resistor? Anyway I'll grab some and see if I can make them work for me. I can swap the tip and ring on the external switch connections easily enough.

https://www.itead.cc/sonoff-wifi-wireles­s-switch.html

Wilberforce!! Those are sweet!! I have the wifi board on my pico!! They are a little overkill for this switching application -- but I'll be grabbing some of those to play with!!

@Wilberforce wow! Hadn't seen those before... (This is probably another thread, but does anyone have any, and have they tried flashing Espruino onto them?)

@user58511 I'm pretty sure you treat it like you'd treat an LED - so a 100 Ohm resistor in series would work great. I think 6V is the maximum voltage you can wire it up backwards at before it breaks (and also the maximum you can put into the diode).

With 100 Ohm resistors you're only really putting 15mA into the diode, so you could drive a whole load of them from the Pico without trouble. They will only switch 50mA on the other side though - so that's not going to drive anything very powerful.

Gordon, I'll have some of Wilberforces' find in a couple of weeks -- I'll start a new thread !

Adapters for surface mount chips. I've had excellent results with them.
They will even buy and mount the chips, or you can buy chips and send them to be mounted.
Lots of SMT to DIP etc.
http://www.proto-advantage.com/store/

I can't claim the sonoff find - it's being discussed on gitter

https://gitter.im/espruino/Espruino

There is now thread here with people testing...

http://forum.espruino.com/conversations/­288230/#comment13033307