Must-haves for EASY DIY controller?

[theatrus]

I2C buses are limited by capacitance, which is limited by the drive strength of the various modules and the pullups. Its not really an external bus - hence I always design in an RS485 transceiver into any external module (that stuff is bulletproof, easily isolated, etc).

However, if you shield the wires, and drop the clock speed (start at 100kHz, and don't be afraid to end up at 1kHz), you should be fine. You can also drop the pullup values provided everything on the bus supports it (I've seen 400ohm pullups on I2C before - its not in the official Phillips spec but will work).

 

[TheFishMan65]

I figured there was a solution. I just had not looked into it yet.

 

[der_wille_zur_macht]

The 400pF cap specified for I2C gets you about 12 feet of twisted pair cable length, iirc. That should be enough for most of us. If not, you can take the measures theatrus suggested.

 

[MaLi]

Hi all.
I hope I'm not interapting, but I have a question.
I bought the following SSR's (for reef controller project), and I think I did a mistake:

http://cgi.ebay.com/SSR25A-SOLID-ST...ontroller-/120584707970?pt=LH_DefaultDomain_0

Are these SSR's trustable? Can I sleep quietly with these SSRs running?
I'm going to connect pumps, skimmer and 300W skimmer (all 220v).

What do you thinik?

Many thanks!
Dan.

Dan,

that's a very nice SSR (kind of expensive though). Nothing that you will be controlling will top 25A !
Being UL listed makes is trustworthy.

cheers,
MaLi

 

[der_wille_zur_macht]

Nothing that you will be controlling will top 25A !

There doesn't appear to be any sort of link to a datasheet from that auction so we can't be sure, but the max rating likely only applies with a huge heatsink and a fan on the relay. If it has no cooling provision and is tucked away in a project box under your tank, I'd probably derate that by 50% or more. Should still be enough for most tank equipment.

 

[danzada]

Thank you all!!!
I really appreciate you help!

 

[der_wille_zur_macht]

Back on topic - for others testing the hardware - I spent some more time troubleshooting the Ethernet interface but didn't get very far. Here's what I know so far:

1) The two defects pointed out earlier in the thread need to be fixed with wire as described
2) Once that is done, it appears that the AVR communicates correctly with the ENC: There is a clock on the SCK line, and data on the MOSI line.
3) The ENC never seems to initialize and doesn't respond - there is never any data back on the MISO line.

The hardware design SEEMS OK, it matches several other successful implementations. The software is definitely OK - I'm running the "ping" sketches included in several of the libraries for this sketch. That makes me wonder if my chip is just fried. Wondering if anyone else has tried theirs with the fixes mentioned above? I may just build another to test freshly.

 

[DustinB]

I haven't started the build yet, but I have extra ENC chips if you need one.

 

[TheFishMan65]

I just found the American DJ power strip for about $23 on ebay for those thinking of going that route. It was refurbished, but I got 2 and that included shipping. I figured I was going to void the warranty anyway .

 

[nauticac4]

terahz and DWZM,

Would this relay board work for the solution that terahz proposed? Just be nice to have everything on one board that could possibly be stuffed into a box with the outlets and such.

http://www.futurlec.com/Relay_8.shtml

I worked a bit on the relay part of the controller so here is the progress.

2x opto-isolated 10A 4 relay board from futurlec
http://www.futurlec.com/Opto_Relay_4.shtml
1x American DJ power strip
http://www.amazon.com/American-DJ-P...8&s=musical-instruments&qid=1278899261&sr=8-1
1x MCP23008 port expander (same as on the controller)
http://mouser.com/ProductDetail/Mic...3008-E-P/?qs=sGAEpiMZZMvcAs5GUBtMdVgPLCS8TUZv

The nice thing about the relay boards is that they come with cables and 2 can be chained together so that you have only one 10 pin cable (8 channels, 5v, gnd)

 

[der_wille_zur_macht]

That would work fine as long as you were not controlling large loads. It's hard to guess without seeing a datasheet, but typically relays are rated under best-case conditions (i.e. lots of cooling!) while we install them under worst-case conditions (i.e. in a sealed box, no cooling). So I would not use anything more than 5 or 6 A on those 10A relays, unless I saw a datasheet that convinced me otherwise.

You'll also need to consider the exact control scheme. Terahz used an MCP23008 port expander which works on the I2C bus already on the Hydra mainboard, and there's code developed - so it's convenient. Otherwise, you could use a different port expander, or just consume 8 I/O pins on the Hydra itself.

When working with relay boards controlling 120v AC, remember - you've got DEADLY voltage in your project now!

 

[nauticac4]

I guess if the board and code are already setup then that the way I am going for fear of the unknown.

If you can beleive it I design capacitors all day but I do the mechanical side of the engineering work and these are high power caps not the little stuff used in electronics like this.

 

[MaLi]

Guys you are going overboard.
For the last 15 months since I built my first Arduino controller I was using SSRs type Gordos M-OAC5-263 which are rated 3A at 120V. I drive a 1/10 HP chiller, 380W of lights, 30 sec. wavemaker powerheads, etc using independent relays and never had a problem. They don't get hot and I don't have them on heat sinks. See my build thread at reefprojects.com.

Ask yourself what you want your controller to drive and target your SSRs accordingly. Beside most receptacle circuits in US are 15A max. So, careful not to burn your house down !

cheers,
MaLi

PS. I got my SSRs on eBay for $1.5/relay

 

[ludnix]

It doesn't seem like they are going overboard considering they are trying to make a universal controller that anyone could use, not ones necessarily tailored to their tank. 10A relays seem perfectly reasonable given it's not known what temperatures they may reach at maximum load.

Someone with a 400w MH or heater would easily exceed the rating of your relays. I think it's reasonable to assume that someone might need up to 5A on an outlet (800w heater would require more still). While yours is designed specifically for your tank and you might not need more than 3A it's definitely not scalable to a large tank.

 

[MaLi]

It doesn't seem like they are going overboard considering they are trying to make a universal controller that anyone could use, not ones necessarily tailored to their tank. 10A relays seem perfectly reasonable given it's not known what temperatures they may reach at maximum load.

Someone with a 400w MH or heater would easily exceed the rating of your relays. I think it's reasonable to assume that someone might need up to 5A on an outlet (800w heater would require more still). While yours is designed specifically for your tank and you might not need more than 3A it's definitely not scalable to a large tank.

hence ...
"Ask yourself what you want your controller to drive and target your SSRs accordingly. Beside most receptacle circuits in US are 15A max. So, careful not to burn your house down !"

cheers,
MaLi

 

[nauticac4]

Got my board today!!! Has the BOM been updated on the code site? Did some fishing through the thread and didn't come across anything.

 

[Ibixable]

I have been trying to get that same answer as well I got the board and now need to start getting the other stuff to put it togather and begin the testing.

 

[der_wille_zur_macht]

Sorry guys, things have been busy. Working on the BOM today. In the meantime, there really aren't any CRITICAL problems with the existing BOM that we know about, so ordering from it won't do any harm - it really just boils down to fitment of the electrolytic caps, finding replacements for a few of the parts that have since gone out of stock, etc.

 

[DustinB]

Is there a relay board or other option than the one from futurlec? Not really into ordering from futurlec unless I have to.

Got my board in(thx dwzm!) and most of the parts. Ordering the last of everything today along with some perialistic pumps.

 

[TheFishMan65]

Dustin, since I was planning on ordering from futurelec can you tell me what issues you had with them. Thanks