thanks for the reply, i was hoping to get some input on this. as far as the rca goes, would the cable i have listed actually work for the AC voltage? You're right those circular molex are expensive, but it would probably even out with having to but all the RCA cables and the 18 RCA jacks. I will have to look into that. Any other suggestions on how to connect the Vac? Preferably something with circular mounts?

I'm sure it would function; the cable and connector can take the voltage no problem. The issue is that it is dangerous and you would be liable if someone got hurt by it. One in 1,000,000 chance, but that one can be serious charges (manslaughter)

I think a circular connector would work, or you could also mount the relay box and the switch box together with screws and run the wires through a ferrule/grommet and have them not be exposed at all.

haha yeah that is a good point, but wouldn't it solve that problem if i didn't use use RCA panel mounts on the relay box and just sent the cable straight through the panel so it could not be removed? that way it could only be unplugged from the power center RCA jacks and the cables would just be permanently connected to the relay box

That would solve the problem.


There are many many cables you could use - Check out the Digikey Catalog. They have an entire section on cables.


You never want to have the live wire exposed when live. That's why receptacles in your house are all female, and the cord is male. Then look at a computer/monitor power cable. The computer end of the cable is female, the computer connector is male. You want a similar arrangement.

Wherever the power is coming from, you want to mount a female connector. Then a male-female cable. Then on wherever the power is going to, you want to mount a male connector.

The digikey catalog also has a section on connectors.


If I could offer a suggestion - I don't recall how many wires you need, but i think your current requirements are very low. Try a D-sub connector (ie: serial, VGA, parallel). They are easily available in all sorts of sizes, genders, mounting, not to mention prefab cables, cable kits, so on, so forth. Good selection.

yeah i have checked the digikey catalog, they have some cables but to order from them you have to get a quote and it then work through it that way which is a huge hassle. i'm looking at possibly using neutrik powercon locking cable connections for this. also the current requirements of the cable need to be enough to handle 110vac perfectly fine in each wire. these cables will be connecting the live power from the switches to the relays. (i think you may be thinking of the cables from the relay to the arduino, which i'm using a TRRS stereo cable for) thanks for the tips though, i guess it's going to come down to finding something that will handle the voltage, be safe, and be cost effective.

wat?

I used to order from digikey all the time, and have never needed to get a quote. Look for parts that are carried in-stock.

my bad you're right, i was thinking of directindustry

Ok, so I registered here just so I could reply to your thread - and that's not a good thing. Since you stated that you have no background in electronics I won't to hard on you; that said: using component video cables for 120v ac ?!?!?!? What the hell are you thinking ??

Next: Why bother mounting the relays in a heatsink enclosure when you've screwed them into a piece of acrylic ?? What sort of heat transfer were you expecting to get ?

Why would you even mount the ss relays in a seperate enclosure ? Why not just mount the on the power centre like the other controller you are basing yours on ? That would save you on wiring wouldn't it ?

I know I sound like a bit of an ####### right now, but let me try to redeem myself a bit.

First off - don't order any ICs. Check out the websites of the manufacturers and request some free samples. TI and ST are amazing for samples - they shipped them to me next day FedEx to CANADA !! And Linear seems very generous with their samples; although they limit you to 2 of each they sent me two DAC ICs worth $55 each and two I2C hot swap ICs worth $25 each.

The way I'd build you system is like this - First off get rid of the switches on the power centre. This should leave you enough room mount the relays on the inside. Try to keep anything with AC as far away and as protected from saltwater as possible. Since you will be using a 16 port expander I would use the remaining 8 ports as inputs and set up 8 tact switches on the front panel in place of the switches that you ripped out to make room for the relays, add some low power LEDs and get instant info on the status of each circuit. Hopefully you got a port expander that has interrupt which will notify the arduino that a button was pushed without wasting clock cycles on polling for button presses. This would give a very quick and very easy to program manual bypass on all circuits. Obviouslly this setup would require you to put the port expander in the power centre, and with the interrupt you need 5 connections - Easy fix though, just use a network cable it has 8 wires.

One thing - don't run more than 3 or 4 feet of cable without an I2C bus extender - I2C is not made for communication over cable. With a pair of extender ICs though; you should be able to run more than 20 feet relliably.

I wouldn't use the OLED screen, especially one that small. It's going to add alot of complexity to your project and especially to your code. Plus the fact that you're going to have to go 6 inches away from the screen to read anything. I would suggest going with a KS0108 based graphic LCD module. They are easilly readable from a distance especially if you use a large font. They also have the added bonus of being cheap - $20 at sparkfun.

My 2c. Take it as you will. One last thing - don't take this too offensivelly but based upon your faillure to grasp some basic concepts as stated in some of your responses I would say excercise EXTREME caution you can very easilly kill yourself with the currents you are dealing with. Most SSRs can be triggered with 3 volts and 5ma; now I'm no expert and by no means can I verify this, would assume that such a small amount of electricity could be conducted over sweaty fingers possibly trigering the SSR and killing you.

alright, a little harsh. i threw this out as an idea to connect the power center to the relay box, the internal cable is an rg-6 coaxial cable that has an internal 18awg insulated wire, which i thought could safely transfer the voltage. i guess not



The heatsink enclosure is by no means to remove heat from the relays, in fact the term heatsink is misleading, it is actually an aluminum box with extremely small fins, therefore called a heatsink box they will barely generate any heat at all. They are being mounted to the acrylic in order to hold them securely in place in the enclosure



I am planning on making this a clean build with three separate parts, yes it would save wiring, however the power center and relay box are going to be displayed and the controller will sit on top of them, therefore i would like it to look clean and do to my design.



Thanks for the tip there



fair enough, i'm going to keep the switches the way i have them though.


only running 18 inches through a cable to the controller box



The OLED screen fits perfectly in my display box, a screen that large would not fit. I have looked at all my screen options and I am currently working with a serial 20x4 character display from sparkfun that i already had on hand. the OLED will be something i will upgrade to. I understand that creating a gui for the OLED screen will add complexity to the code, however that's part of the fun!



i did say that i have no electronics background, everything i have learned about this is from doing research and gathering data from other projects, i'm putting this together piece by piece and i could use help with different aspects of the project, please feel free to add constructive criticism to my build

Sorry if I come across as bashing - I'm usually very blunt with my comments and give people that perception. I felt I was putting forward some constructive criticism.

If you are intent on remote mounting the SSRs away from the power centre, I can only recommend that you mount them in a fully sealed enclosure. For interconnect I would strongly advise against anything "quick connect", make those connections permanent and sturdy. Home depot will sell cable use to make extension cords by the foot. That would be the best option in my opinion. Don't forget, you can run a common neutral across all 8 relays.

BTW..If you go with that OLED, you don't need the Arduino. You can use the onboard MCU on the OLED module to control everything. I was looking at the larger 2.4 touchscreen for another one of my projects. The language seems pretty easy to learn too - Something to think about.

no problem, i would rather be called out then learn the hard way. this is what i will be mounting the SSR's in, and i am going to have a end panel for each side. i am using the 4'' model of this box to mount the controller parts in(arduino, screen, rtc, cable inputs, breadboard) yeah i know i wouldn't need the arduino, but it would be easier to control it in serial from arduino and use that for the pins and code/etc. i think it may be possible to use the 4dgl graphics language to create the gui then run it with arduino? am i right about that? also i think these powercon cables/mounts would work for the Vac, use 3 cables with mounts on the power center and relay box to transfer 9 wires.

cable
http://www.sjmediasystem.com/pwrcn20-ab-3.html
inputs
A
B

Yeah, those would work, but the question is Why ?? Look it's your project and you can do it any way you like. But $90 for the cables, $20 for the connectors, another $25 for the heatsink box, add in the price of the arduino, the Power centre and the 20x4 LCD plus shipping for everything. What's the point of a DIY if it's going to cost you twice that of a commercial solution ?

You can buy from digikey or mouser the same 120V plugs that are on the AD Power centre for $1 apiece. mount those in your project...done! How much cleaner of a setup do you need ? Check ebay - you can get much bigger project box for half the price of the one you have with free shipping from china. They have some that the end plates have tabs so you can mount it inside your stand - slick setup. Hide the switching box and remote mount the lcd within easy view, now THAT is a clean setup.

I also just realized you wrote in your reply that the SSRs wont make much heat. On the contrary, you must mount them to something metallic as they produce alot of heat. A SSR is an enclosure that contains an optocoupler and a TRIAC or MOSFET. The more current pulled through them, the more heat they generate. You are aware that when an SSR fails, it typically happens with a short on the output. Best to build in some extra protection if you use it for ATO. I plan to use a mechanical relay on the same line for peace of mind. And no, you would NOT be able to use two SSRs because the output side draws it's power from the line it is switching; which means that if you put two of them on the same line, neither would be able to switch on - using the mechanical allows the SSR to switch on - as long as the mechanical is switched first.

yeah i know, i will most likely not do that because it is costly. but DIY part of the project is the best part about it. i would rather have a controller i could completely control and write code to do anything i want rather than a commercial controller of the same price. also i don't have a stand to mount anything to or hide any parts. this setup will have to be out in the open because the tank sits on a dresser at school. As far as the heat for the SSR's the heat should not be very high, you're right, it would make more sense to just mount them to metal, which i am thinking i will do. (i am rethinking my whole heatsink box design and setup after your input) however the relays are rated for 25amps, and nothing i will have plugged in will be over 3amps. with such a low draw on a capable relay the heat should not be very siginificant (correct me if i'm wrong). also the float switch from the ato will be plugged into the arduino pins which will then trigger the relay when it is low, however i am planning on writing into the code to only allow it to remain on for 10 seconds at a time and a total limit of 6 times per hour. also there will be an alarm and led light that will come on if something fails in the system so i can catch it and fix it.

here is the data sheet for the relays (model # GN 84134010)
http://www.crouzet-usa.com/catalog/gordos/gnssr.pdf

If the SSR fails in a short, it doesn't matter if you have a limit programmed in software because the relay will flow power regardless of state of the input. For me that really wouldn't be a huge problem because even though I use a 5 gallon pail as a reservoir, it wouldn't make any difference if it all got dumped at once - My total system volume is in excess of 220 gallons, when you start dealing with nano tanks that could easilly have system volumes smaller than the ATO reservoir - a small failure could spell disaster.

It amazes me how everybody (In general - not trying to pick you) has to build in so much redundancy into the ATO system - duplicate float switches and max level switches and software limits and this and that; but you never hear anybody mention "what if the relay fails on ??"

alright so you're saying to wire in a mechanical relay before the SSR for the ATO. thanks for the tip, on my tank it would be terrible if it pumped all the ro water into the tank. the tank is about 3 gallons and the ATO container is 1 gallon.

i am looking around for a different relay box enclosure, i think i am going to try to find one i can mount directly to the top of the power center using screws and then drill a hole in the bottom of the box and the top of the power center to send the wires through to the relays. it would completely contain the ac power and no jacks or cables would be needed.
(i looked at the boxes on ebay from china you suggested, they actually are a really good price, but i could not find one long enough to fit all the relays in one)

this style box at 10'' or more would work great, it has a flat metal bottom to mount the relays i'm waiting for a reply from the company
http://gkphotonics.com/gk5.html

got the 10'' project box from gkphotonics, so i'm waiting for that to come in.

just got heatsink box in the mail for the relays, great price and fits them perfectly. also comes with end plates

that is nice, how much for the box ?

$20 shipped for 10'' box and end panels (included screws)

nice, that's pretty cheap - gonna check with them and see the price for shipping to canada

what are you building?

What else is there to build ? An arduino based controller !!

Just something for my lighting and temp though. I'm going to be running four dimmable t5 ballasts in an eight bulb Tek light fixture. I want to be able to dim in sets of 2 lights to have the ability to mix the colour of the bulbs and dimming rate of each colour to mimic a sunrise/sunset. I also plan to vary the day length and water temperate to match the conditions in the enviroment - I was able to find a couple of sites that give historical ocean temperature data from in and around fiji. As well, it's pretty easy to find info on sunrise/set times and day length for any location in the world.

My hope is that in replicating temperature, moon cycles and daylight times I can get sexual coral reproduction to happen in my tank.

nice, what size tank? got any links to it?

120 short - 48x24x24

No, no links. I'm not keeping track of my build. I'll probably post something up after I'm done.I did a few prototypes on an arduino protoshield and now I'm building my circuit on a protoboard. When I'm done with the circuit, I'm just going to burn an atmega8 with the sketch, leaving out the bootloader. I figure 8k should be more than enough for what I want to do.

I built in an icsp header so I can program the atmega8 with my duemilanove's ftdi chip in bitbang mode.

One thing I'm debating about is getting a linksys router with dd-wrt loaded on it and connecting the serial on it to the arduino, that way I could use the router's web server with a couple of cgi scripts for web monitoring of my tank without needing to write a whole bunch of code and needing to upgrade to at least an atmega328 and redoing my circuit to use an ethernet controller chip.

that sounds complicated but but it seems like a sweet build. i would be interested to see it once you finish, especially with the router if you use that. my build has been slow due to other expenses and work in general

sounds more complicated than it is; if you can write an arduino sketch - you can flash a bare chip.

Just dive in headlong and get a few spares

before I started, I had limited soldering experience. By limited, I mean limited to soldering two coppers pipes together (badly, I might add). For this project, I've soldered 0.5 mil pitch smd components (very well, i might add)

Trial and error is much cheaper if you managed to swag some free samples !!

finally got some wire i ordered about two weeks ago in the mail today, now i can work on wiring the relays and switches and connecting the heatsink to the main fixture

build has been going very slowly due to spring break and class projects

How dare you focus on the important things in life.

update: still really haven't done much work with this, school has been extremely busy. most likely i will implement the LED dimming with the arduino first just to get that part functioning before the whole thing is put together. i am currently working on putting the whole build on heathbox.com

The i2c spec supports 127 addresses and depending on the microcontroller implementation of i2c you can actually sneak in 255. However, it only allows for 400 pF of capacitance on the entire i2c bus. Each device on the i2c bus contributes approximately 10 pF of load and 10 pF of circuit board trace capacitance. Cabling contributes 50 - 100 pF per meter.

So, at best, one could put 40 devices on an i2c bus if all the devices were on the same circuit board. Add any cabling at all, e.g. from a controller box to an outlet switcher box, and the number of supportable devices drops precipitously.

However, there's a chip for that. The P82B715 (Phillips or TI) can be used as a bus extender. Before your cable leaves the box, put one of these at the exit and connect your cable to it. At the other end, put another one. It can extend i2c across some ridiculous number of meters of cable, and they can be connected together in a star topology, allowing one to branch the cable to both an outlet box and an LED driver box. The P82B96 serves a similar function with some extra bells and wheelbarrows.

Instead of bus expanders, you may wish to consider using an ATtiny25 at each destination point on the i2c bus. It will cost a little bit more, but the ATtiny25 is only $1.20 each if you buy 25 of them. The ATtiny25 has two pins which will perform i2c functions. You can also follow the instructions in this application note:
AVR Zero Cross Detector
to use the ATtiny to detect when the voltage in the mains is crossing zero and have your relays only switch at that point. This can avoid some nasty voltage spikes caused when the relay attempts to make a non-zero current instantaneously change.

Store an address in each ATtiny's EEPROM for it to use on the i2c bus. Send it a command from the controller to turn the mains off or on, and program it to wait until a zero crossing to do the deed.