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Author Topic: remotely controlled power switch?  (Read 31557 times)
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August 27, 2011, 07:17:18 AM

Pipesnake: ETA is mid-September.

BkkCoins: There is only 15 usable digital outputs on the PIC-WEB's EXT connector ($50 in the US). Plus you would have to design a separate board for the SSRs and their resistors ($15). In the end it would be twice more expensive per controllable computer ($65 for 15 computers) compared to my solution ($100 for 45 computers).

About those 4 things:
- I want SSRs because I want the electrical circuits to be isolated, for safety. A motherboard or PSU going up in smoke and sending voltage spikes through the power switch wires shouldn't fry my AVR or the 44 other remote-controlled computers...

You can use any optoisolator, doesn't have to be an optotriac.    

Find me, on Digikey, any type of opto-isolator comparable to my SSR: $0.75 or less for quantities of one hundred, and that operates with an input current of 1mA. I would be delighted to be shown there is one.

- If using transistors, the user would have to know which pin of the power switch is + and which is -, increasing setup complexity for non-technical users.
If they cannot figure out which pin is the pos/neg [...]

I may sell assembled kits and don't want to tell my clients "GTFO if you don't have a multimeter". I am like Steve Jobs, I care about ease of use Smiley

- My SSRs are cheap ($0.75 in my quantities)
Sounds like you are buying the optotriacs...small components of SSR's that are use to trigger the bigger Triacs in a SSR circuit.  If you were building an SSR that would switch the PSU current you would be looking at around $5/SSR minus the board (and snubber).

Nope. These are plain standard SSRs. Just go look them up on Digikey, there are plenty in this price range. Once again, I am controlling 5VDC, not 120VAC.

Also, have you tested this.  Every time I try to run DC with a Triac it will turn on but it will stick because it requires a negative voltage swing to trigger turn off.  So basically you will trigger it and it will hold the power on.

A quick google search verified what I thought.  Triacs (SSR's) do not properly trigger DC.

So looks like you will have to either use small relays with transistor drivers, DC optoisolators, or just transistors as I was saying before.

I have not seen this pb. When I stop applying voltage, the SSR output circuit opens...

If it works for you it works it, sell it.  I was just offering solutions which are easy and cheap I am not trying to sell kits, but I am planning an Instructable on the topic.  You could make a simple connector which has to be pinned in just like if you were pinning a case switch, my point is that if someone cannot properly pin a Mobo power switch they probably shouldn't be trying to setup a multi computer remote reset. A multimeter should be in every large scale miners possession...if not you do not have the proper tools.  They are like 5 bucks for a cheapo one at Harbor freight that would be good enough for checking the pins.  If you actually buy a decent one it becomes more useful for things like checking PSU voltages and other things.

As far as difficulty finding which pin on the Mobo pinout is the power switch(-) its the one of the 2 that is ground...that easy, all the power switch does is ground a +5v pin.  You can test this with the computer off, just connect one lead of the multimeter to any mobo screw and touch the other lead to the power switch pins til it reads 0 ohms and that is the switch negative.

Which part number "SSR" are you using.  An optotriac (which is a small ssr in itself but is commonly used for driving large triacs) like the MOC3023 runs .33c per unit at the single unit price.  Something like the MOC8016 should work (didn't look too hard at it but I think it would work) is $5.60/10 units...but you still have the polarity issue.  If you sink the drive current to the AVR (active low) from the optoisolator the current to drive it shouldn't be an issue.

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