AlanM

Drain and returns in the middle of the tank.

I think I don't have to worry about blowing the driver. If I short the dimmer wires together, the highest current observed, with 2.5mA going through the dimmer wires, is at all the way dim and that's when you see a flicker. If I then open up the dimmer wires, so current is 0mA it goes as bright as it can. The driver maxes out at 530mA, btw. Wonder if an audio or log taper instead of a linear taper one would do something good.

Made some progress. So I used some parts from work to look at the little circuit that the potentiometer is attached to. It's a 500k Ohm pot that Evergrow supplies on their board. The number doesn't really matter, just that it's really really high compared to the internal resistance. When it's that high no current flows through the board (actually, a couple microAmps) and the light is fully on. When you turn the pot all the way down to 0 a resistor on the board prevents it from going all the way to 0 and keeps it at about 280 Ohms which is just a bit up above the dimmest level allowed. If you go all the way dim at 0 Ohms you start to see the lights flicker a bit which would annoy the heck out of people. The problem is that it's not linear. With a 10k pot I can go from all the way dim at 0 to almost all the way bright at 10k with most of the dimming happening between 0 and 2k, but then if I pull the pot off, to make the jump from 10k to infinite resistance, it gets just a bit brighter. So all of that circuit is for linearizing the dimming function. It gives finer control at lower Ohm resistance and much coarser control at high resistance so that you can go from full off to full bright while maintaining a useful range of dimming over the entire travel of the knob. Would it be useful for folks if I had it go from like 0 to 90% brightness under control and then full on for the last 10% (by opening the circuit)?

I am always surprised that the water just off the coast of Long Island is clean enough to put in your tank. Shouldn't it be full of fertilizer runoff, pharmaceuticals, industrial solvents, and shredded toilet paper? We go to Rehoboth Beach in Deleware each summer, should I scrape up some of that beach for the tank?

Right. I think theyre probably doing something cheap and reliable, but just not something Im familiar with. Our electrical engineer here was puzzled by the circuit. Sent me home with more things to measure on the working one.

By the way, digital pot won't work either because it's a 500k Ohm pot, which doesn't exist as a digital one, so it would have to be something more exotic.

OK. I think I know how the little circuit board with the pot works. Or at least I think I do. It actually uses a change in current to dim the driver. I was measuring a 0-10V difference across the pinouts when dimming to 0 or to max power, but that was an Ohm's Law effect of what was happening with the current. Took me a while to figure out why they needed a little transistor on that board (the tiny square black thing in the middle with V+ on top of it). So it's not as easy as just supplying 0-10V on those two pins. I'd have to supply a fixed current along there, which isn't so easy. I'll pull the pot off the board, see what the rating is, and see if I can't drive it from a ditigal pot like I'd originally planned. DaveS, I could be wrong, but I think it's easy to do number 1 above. I snipped the two wires that control the dimming, the bottom two on the far right in my picture, and the light was happily on full bright and the fans were running. Replacing an a physical pot with a digital one won't necessarily work. Sometimes the digital pot gets pissed if the loads connected to the output resistance pins are referenced to a way different voltage than the signal and control inputs to the digital pot chip. That FET is probably a better way to do it than with a digital pot and arduino board etc. Could do it on one chip if you got one that would give you the right input and output ranges.

That channel still sort of works. And I've got one from the other channel to be more careful with. I'm pretty confident that I can figure it out, and once I figure it out I won't need this pot, so it should be fine.

haha, well I let the magic smoke out of the little circuit board pictured above doing some testing with a battery. Hmm. I should be more careful. Still playing with it.

I believe you'd do both. Silicone along the edge, smoosh the pieces together, and then put a cover bead in the corner after assembly to protect the edge silicone. At least that's how glass tanks are built. I'm not in any way a tank builder, so maybe Jeff the PimpedOut Naga can answer. 8)

Ok. Will try some stuff tomorrow. Will just twist in some wires for now and if it works will make a cleaner solution. That can be put back to factory config easier.

OK. So here is the pic of the potentiometer board: The pot is a 5-pin one which has an on off switch which are the two pins under the AMC and the 3 pins just over the surface mount resistors on the bottom vary the resistance. I'd planned to replace that pot with a digital one. It seems to be a 500k Ohm one. But then I saw the VDIM+ and the VDIM- which I've labeled Pin1 and Pin2. When the lights are on all the way dim I get 0.5V across those, when they're on all the way bright I get 9.8V across those. There are 4 wires coming out of this little board going into the driver which I think are vdim+, vdim-, fan, and ground. I think if I just put a 0-10V signal on the first two pins from the Apex or ReefKeeper I could dim these things and leave the pot alone. No arduino or digital pot needed. Marco, was there a place where people were trying to hack these things and ran into fan problems? I could see a problem if it was actually running some current through these vdim+ and vdim- pins, but at least on mine the fan speed doesn't seem to vary with the dimmer knob. I can at least put a little pot on a 9V battery to see if I can dim them that way so I don't risk drawing too much current from my Apex.

right. I have it open now, and I can see that the board the pot is connected to is a bit more complicated than just providing a dimming voltage.

If the ReefKeeper Lite Plus has analog outputs it seems like it should work just fine. This would just be replacing the knobs with a digital one that's addressable from an Arduino. I'm going to do a little bit of teardown of my D120 to make sure the forum guys talking about attempting this know what they're talking about. I think it would involve de-soldering the pots from the D120, but maybe I could just put the ditigal pot in parallel with the knob and add a little socket to connect a controller. Then you'd just turn on the knobs to minimum brightness and leave it there while the controller did the rest. If you wanted it all the way off you'd have to switch off the socket it was connected to.

Well, the 5206 has 6 pots, 12 D120's have a total of 24 pots, so you'd need 4 of em and 4 arduino boards. Wouldn't need that many channels on the apex though because those supply a voltage rather than a resistance. Actually, maybe I'll take apart my D120 and see what voltage is across that pot to see if a voltage would just work.

I'm working on a circuit to use an Arduino Uno and a digital potentiometer to allow an Apex to do dimming on a D120. Is this something folks would be interested in? Would cost about $40-50 for parts to control 6 channels of D120's, so 3 D120 units total. Edit: Would do this: http://arduino.cc/en/Tutorial/SPIDigitalPot with the chip shown in that article. Apparently the D120's use a 10k potentiometer to do the dimming, so the AD5206 has 6 channels of 10k resistors.

Beyond the concern for fish welfare, I couldn't take the choreographed ignorance of the main characters in that show. If those dummies on either Tanked or Fish Tank Kings actually ran a successful business without the TV show I'd be really surprised. I hope "dumb" is just a character they play on TV, not in real life. Also, I can't watch any of the current crop of over-produced and edited reality shows that only give you 5 minutes of content in 30 minutes and fill the rest with commercials and repetitions of zoom/pan shots or recaps of what you just saw before the commercial break.

I kind of can't wait to see this thing. With the discussion about the Tanked goombas doing it wrong, it will be fun to see it really done right.

Last July I was putting ice into my freshwater tank double-bagged in ziploc to try to keep the fish cool during the week of no power after the derecho. It was a pain. Maybe I should make some RO icecubes in case it happens again.

We have used Big Green movers twice in the past 6 years and they were great both times. No big tanks were moved, but they charge by the hour and showed up with three guys that RAN with our boxes the whole time so as not to waste time. They were really good. Also brought lots of boxes and paper delivered in advance and only charged us for the ones we used. And then gave credit for any used boxes we returned a week later in good shape so they didnt end up in the trash.

those things are so big they're going to compete with the fish for blackworms!

Tom, weren't you saying something about how you had to put extra extra screen over the outside part of the air intake to keep out the spiders and such?

Your tank is a beauty. It's amazing to see the difference from page 1 where you're asking about the goo growing on the sandbed to now.

We have buried power but somehow lose power frequently. No idea what that's about. I do enjoy the no power lines thing in our neighborhood, but don't seem to be getting the benefit of no outages.

Sounds like VA got the hammer and MD and DC were spared.