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DIY Project Desktop Pico/Mini Acrylic Tank

noodlesuk

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I have been following recent threads with mini/Pico tanks, always on the lookout for a new project, so thought I'd try and build a small acrylic tank for plants only. I'm lucky enough to have access to a laser cutter, so designed up a 140mm cube design, with integral back sponge filter. Top will likely be a simple sheet, with integral white LEDs, again, USB powered. A small USB pump will pull water in through the baffle, up through the sponge and out at the top. Might need some sort of spray bar, depending on the pump output and play about with the inlet to get the flow correct.

Using Tensol 12 to weld the sides together. As the tank is so small, a large toolmakers angle plate was really useful for holding the sides perpendicular to the base, a strong magnet on the inside, kept it all flush. Lots of videos on YouTube show the Acrylic adhesive being 'wicked' into the joint, via capillary action, giving a crystal clear joint with no bead. I found the Tensol 12 to be too viscous for this, it appears to have some gap filling properties, so had to apply it rather a bit like silicone in a bead. Not the nice clear finish I was looking for, but will be ok for a first off. I also found the lasercut edges of the cut parts had too much of an angle on the edge, to bond without finishing. The filling properties of the Tensol, wasn't quite enough. Lasercut parts always have a small angle on the cut (~5Deg, assuming this is due to refraction) which I removed using wet and dry and a flat offcut of Acrylic. The baffle face was also finished with wet and dry, to give a matte texture, think this looks better than the usual gloss face finish.

Next step is to finish off all the bonding, fit and bond the baffle, then fit and test out the pump.
 

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noodlesuk

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After curing for 12hours or so, quick leak test, very small leak in the corner that needs some more adhesive, otherwise pretty good.

Pump works well, bit on the powerful side, but adding the sponge should reduce the flow.

Edit - Couldn't resist getting some soil in there and some flint (which might not be very suitable, will investigate) from my lunchtime walk, needs more depth, maybe larger hardscape, will have a play.
 

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Andrew Butler

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Love it, a bit small for my liking but the concept is great.
What rating is that pump and dimensions? I might be able to help but have a feeling it will be around the same as what you have, although I've some fittings that might allow you to plumb it and regulate.
 

noodlesuk

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Love it, a bit small for my liking but the concept is great.
What rating is that pump and dimensions? I might be able to help but have a feeling it will be around the same as what you have, although I've some fittings that might allow you to plumb it and regulate.
Thanks for the comments. The pump is rated at 200lph and has some flow adjustment with a sliding damper. Outlet is 8mm.

USB Pump

It seems to work quite well. It looks a little precarious in the tank, but the sucker pads just about fix it on the back and the outlet is a snug fit in the baffle. I did think about a spray bar, but I think I might just use a second flat baffle a few mm from the outlet, if I want to diffuse the flow. I think for what I need, it should be just a out right, thanks for the offer of parts though.
 
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ScareCrow

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Nice project, I've never used Tensol 12 but would like to build an acrylic tank one day. I'm not sure what the properties of Tensol 12 are but to make spray paint and acf50 flow more easily, I normally stick it in a bucket of warm water for a while before I use it. I don't know if this would work with Tensol 12.
With regard to the flow, what if you were to divert some flow into the back chamber. You could drill a small hole in the outlet, before it goes through the back chamber. If you wanted to make it adjustable and you have a piece of pipe that will go over the outlet pipe between the pump and back chamber, you could drill a hole through the outer pipe and the outlet so that they align. Then when you twist the outer pipe it increases or decreases the opening size. Hopefully that makes sense!
 

noodlesuk

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Nice project, I've never used Tensol 12 but would like to build an acrylic tank one day. I'm not sure what the properties of Tensol 12 are but to make spray paint and acf50 flow more easily, I normally stick it in a bucket of warm water for a while before I use it. I don't know if this would work with Tensol 12.
With regard to the flow, what if you were to divert some flow into the back chamber. You could drill a small hole in the outlet, before it goes through the back chamber. If you wanted to make it adjustable and you have a piece of pipe that will go over the outlet pipe between the pump and back chamber, you could drill a hole through the outer pipe and the outlet so that they align. Then when you twist the outer pipe it increases or decreases the opening size. Hopefully that makes sense!
Thanks, that's a good idea with the Tensol, am planning to build another tank soon, so will give that a go. Nice and simple to try too. Yes I see what you mean about the outlet control, that makes sense and is a nice elegant way to control the flow, will see how it goes. Thank you
 

Gill

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This is a great little project, And you have a laser cutter. So are able to make any shape of pico tank.
That pump is great, they are mainly used for the Solar powered water features. And I used them on the Nano Pond.
 

noodlesuk

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Minor update, added some LEDs and a small 3.3v regulator to run them from USB. Need to cut the cover for LEDs and tidy up the cables, thinking of adding a cable gland/clamp in the LED cover. Quite happy with the brightness. Excuse the very sorry looking dwarf Sag. bit short on plants to put in, added some floaters and Pearl Weed to get it going.
 

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noodlesuk

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Minor update, added a Trinket Arduino based controller to the LEDs. Excuse the sloppy soldering, was using the portable iron.

Controller fades in the LEDs at 9am, then out again in the evening. Next job is a cover, to hide all the wiring!
 

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noodlesuk

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Small update, PCBs arrived to tidy up the light. Added a few more LEDs. Just the one mistake in the routing, pulling the Trinket USB IO high, had to remove some pins. V2 will have some buttons to control LED intensity manually.
 

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nayr88

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Very impressive!
Just came over from the donation advert you had up and it’s very tempting but I have never taken in a pico tank, this is around 2 litres righ?

Are you taking on commissions for other size tanks? I really think there could be more market for this on here especially with the hidden wall for filter and heater! Maybe even and shelved tank for people to try the shallow look with the shelf being for emergent growth.
 

noodlesuk

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Very impressive!
Just came over from the donation advert you had up and it’s very tempting but I have never taken in a pico tank, this is around 2 litres righ?

Are you taking on commissions for other size tanks? I really think there could be more market for this on here especially with the hidden wall for filter and heater! Maybe even and shelved tank for people to try the shallow look with the shelf being for emergent growth.
Yes, about 2.5L. Maybe sounds like an interesting project. What sort of size? Have you any examples?
 

nayr88

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I’ll come back this evening with some examples or at least a sketch up of what I mean
 

zozo

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Small update, PCBs arrived to tidy up the light. Added a few more LEDs. Just the one mistake in the routing, pulling the Trinket USB IO high, had to remove some pins. V2 will have some buttons to control LED intensity manually.

Nice little project... :) Do you have a link to the trinket code? And what is the LED type you use? I don't see any current limiting resistor on your PCB. Are these build in the LED?
 

noodlesuk

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Nice little project... :) Do you have a link to the trinket code? And what is the LED type you use? I don't see any current limiting resistor on your PCB. Are these build in the LED?
I'll send you the code I wrote. I selected LEDs with a 3.3v forward voltage, then used a 5v to 3.3 regulator, which is switched to the LEDs by the MOSFET.
 

zozo

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Thank you!... :)

Regarding the LEDs, I did have the exact same idea and thought in my design why a resistor for a 3.3 volt LED if I can have a 3.3v supply, till an expert on the Arduino community saw my diagram and he said it still ain't recommended to do this. Because nothing in the world is perfect, LEDs have tolerances in forward voltage and regulators have tolerances in supply voltage due to temperature differences. Then if the regulator provides 3.4 volts instead the current through the LED will rise exponentially if it's a 20mA LED to 40mA because the diode itself has very little resistance averagely 13 Ohms only and it might shorten the LEDs lifespan significantly running the LED over its peak current specifications.

That it is best practice to always have a voltage drop and use a current limiting resistor. Then a power peak of 0.1 volts will not cause such a drastic high current flow over the LED.

If it's a 3.3v - 20mA LED
Since 5-3.3=1.7v/20mA = 85 Ohms then if the regulator or supply peaks at 1.71/85=0.0201mA. The resistor never allows more current flow.

It can work with 3.3v cell batteries because the internal resistor from the battery limits the current. But constant voltage power supplies don't.

Thus I didn't take my chances and changed my design before I put everything on the PCB and now I'm running the LEDs with a resistor for each LED on the VCC 5v.
 
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noodlesuk

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Thank you!... :)

Regarding the LEDs, I did have the exact same idea and thought in my design why a resistor for a 3.3 volt LED if I can have a 3.3v supply, till an expert on the Arduino community saw my diagram and he said it still ain't recommended to do this. Because nothing in the world is perfect, LEDs have tolerances in forward voltage and regulators have tolerances in supply voltage due to temperature differences. Then if the regulator provides 3.4 volts instead the current through the LED will rise exponentially if it's a 20mA LED to 40mA because the diode itself has very little resistance averagely 13 Ohms only and it might shorten the LEDs lifespan significantly running the LED over its peak current specifications.

That it is best practice to always have a voltage drop and use a current limiting resistor. Then a power peak of 0.1 volts will not cause such a drastic high current flow over the LED.

If it's a 3.3v - 20mA LED
Since 5-3.3=1.7v/20mA = 85 Ohms then if the regulator or supply peaks at 1.71/85=0.0201mA. The resistor never allows more current flow.

It can work with 3.3v cell batteries because the internal resistor from the battery limits the current. But constant voltage power supplies don't.

Thus I didn't take my chances and changed my design before I put everything on the PCB and now I'm running the LEDs with a resistor for each LED on the VCC 5v.
That's good to know, the LEDs I have can take quite a bit of pulsed current and the reg is fairly high precision. But will look at adding a resistor on the V2 PCB.
 

zozo

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That's good to know, the LEDs I have can take quite a bit of pulsed current and the reg is fairly high precision. But will look at adding a resistor on the V2 PCB.

Electronics are nowadays indeed very precise, I guess it's a better safe than the sorry theory... :) After getting this advice I dove a little deeper into this story... And it was also said that if you combine a bunch of LEDs in a circuit it is best to always use LEDs and other components from the same supplier and production batch. Because tolerances can differ quite a lot.

But since I'm running my circuit on a power bank I got confirmation that it indeed holds true even without any measuring equipment for such small currents. My 5volt power bank needs about 100mA current draw to stay active, below this draw it will shut off automatically. This is shown on the power bank with indicator lights. When switched on, the battery indicator lights up and as long as the connected device is drawing 100mA or more the indicator lights stay on. When the current draw goes below 100mA the indicator lights go off after 3 seconds and 110 seconds later the power bank switches off. To determine the needed current I kept adding 200 ohms resistors parallel to the PB, I ended up needing 4, this makes 5v/200=25mA x 4=100mA current draw to keep the power bank staying alive.

When I hooked a 3.3v voltage regulator and 3 LEDs with a 3.3fv x 20mA to the power bank I theoretically should not have much more than 65mA current draw with 3 LEDs and regulator combined. I didn't measure how much exactly but noticed the power bank didn't switch off and it stayed active. This confirmed the 3 LEDs were drawing over 100mA together. After adding current limiting resistors it did switch off again. :)

Must add the LEDs even rated at 20mA did stay on for 14 days connected directly, still didn't get hot and I didn't wait to see at what point they would burn out. Could still be that the rated lifespan at 50.000 hours shortened is about neglectable. I didn't want to wait that long to see where it ends and I just went the generally accepted theory limiting the current over the LEDs. :)
 
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