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I just bought from ebay 111ager SSR 3-32VDC input power supply with load current upto 5A @ 5-220VDC. Link to the product: (https://goo.gl/MOkAU3).

I wanted to use it to control a 5VDC@2.1A load using Arduino UNO. I didn't connect any external component as I thought the SSR should do the task it is designed for without having to include external electrical components.

The code in the arduino puts high the SSR pin for 10 seconds and then turns it low for 5 seconds. I connected my smartphone (samsung galaxy S6) on the load side. And here is what happens: My phone just blinks without charging after each 5 second the SSR is LOW. The picture below shows the connection diagram.

enter image description here

My guess was that the phone is not getting enough current from the USB power supply as the SSR probably has higher resistance. But I don't know what I should do. Any kind of comment/suggestion is quite welcome.

[PS: I connected the SSR input at 5V DC of the Arduino. The same things happens with the 3.3v of the arduino]

Look forward!

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  • \$\begingroup\$ Show pictorially how you connected the load and please provide a proper data sheet link to the alleged solid state relay named as GJ-5FA-L on the product you linked. \$\endgroup\$ – Andy aka Dec 10 '16 at 12:05
  • \$\begingroup\$ also, please use a better title that describes your problem \$\endgroup\$ – Marcus Müller Dec 10 '16 at 12:14
  • \$\begingroup\$ Andy and Marcus, thanks for the feedback. This is my first post on the forum and I will improve in the future. I just could not find the datasheet for GJ-5FA-L on the internet. Some description can be found on the arduino forum (forum.arduino.cc/index.php?topic=231045.0) \$\endgroup\$ – maranatha Dec 10 '16 at 13:16
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    \$\begingroup\$ looks like a perfect example of a nefarious part . Mager Company register in China about 1 yr ago , has no website ( formerly WENZHOU TAICHUAN ELECTRIC CO., LIMITED registered www.tceele.com but never created), no legitimate specs and very little eng. credible information. Observe these characteristics and recalibrate your judgement in future. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Dec 10 '16 at 13:35
  • \$\begingroup\$ more nefarious info ebay.com/itm/… Trigger: high level trigger, 3-32VDC relay switches on (ON), 0-0.5V relay is switched off (OFF) 0.5-2.5 volts unknown state does not look like SSR but fake relay specs.. try 12V \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Dec 10 '16 at 13:50
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If the rough specifications that are available for the relay are correct, then it is not suitable for your task.

  • ON the relay image on the site you quote the usable voltage range is shown as 5-220 VDC.

  • This stack exchange question and answer from 2014 Arduino SSR 5V DC (Mager GJ-3FA-L) indicates tat the relay is for use with 5V-220VDC and has a typically 2.5 VDC dro on the load side when on.

So - you are trying to use the relay with a voltage that is higher than the minimum allowed by the USB spec (ie 5V). Designs MUST ALWAYS use worst case specifications.

Even if it worked at USB vltages, the 2.5V drop wil make it completely unsuited to your application.

Measuring the on-voltage-drop with a meter will allow you to better determine the actual drop.

Metallic contact relays are still, in many cases, and apparently including this one. a better solution than are SSRs. Alas.

You could make a switch that met your need using a suitable MOSFET and perhaps an optocoupler if you need good isolation.

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  • \$\begingroup\$ Hi Russell: Do you mean electromechanical relays by metallic contact relays? I have used them and they work fine. It is just that I worried they might tear down easily. I also bought FOD3184V optocouplers but didn't succeed in making it work. \$\endgroup\$ – maranatha Dec 10 '16 at 13:43
  • \$\begingroup\$ @maranatha you must specify DC ohm resistance or peak current, you may need a 10A relay to handle surge . Just use a 10~20A MOSFET Pch \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Dec 10 '16 at 13:56
  • \$\begingroup\$ @maranatha Yes. Metallic contact relays. Still very good in many applications. As Tony says - a MOSFET is a good solution given a suitable circuit. \$\endgroup\$ – Russell McMahon Dec 11 '16 at 23:23
  • \$\begingroup\$ @Tony Do you have any MOSFET model that you suggest? It would be really helpful. \$\endgroup\$ – maranatha Dec 12 '16 at 15:48
  • \$\begingroup\$ @Russel, I had a 3A optocoupler (FOD3184). But this did not also switch on my load. Do I have to look for an optocoupler with higher current rating? What is really key thing to consider when buying an optocoupler for 2.1A@5VDC load? \$\endgroup\$ – maranatha Dec 12 '16 at 15:52

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