Underwurldes - Diy Auto Top Off Project

[sophos9]

I 'guessed' early on in the project that they were normally open switches - phew, got that right as normally my luck dictates that a 50/50 chance means I usually choose the wrong option...


Andy

Hi mate, good guess! The sensors can be normally open or normally closed so we would have been OK - I think?

Yea I remember, just lost the plot!

Will get it running in the tank tonight (*fingers crossed*) and get some photos up - cant wait for not having to top off the water

 

[SkiFletch]

Hi Ski,

Wiring them in series allows both switches to have activated to complete the circuit however only one switch has to deactivate to break it...

What if one sticks open? The circuit will never be activated...

 

[Underwurlde]

...thus failing SAFE. You'll know it's not working because of the necessity for manual topping up.

Andy

 

[SkiFletch]

Wait a minute, am I backwards here? . If both switches are normally open that means they're open when the float is down or up? And which way is the circuit wired; switches open = off, switches closed = filling; or is it the other way around?

Lol, so easy to get this backwards

 

[Underwurlde]

I don't have access to any float switches but here's my guesstimate:

If both switches are normally open that means they're open when the float is down or up?

Up (water level OK).

And which way is the circuit wired; switches open = off, switches closed = filling

Correct.

When the tank is nice & full of water, the switch is OPEN
When the tank is getting empty, the swich(s) CLOSE

For simplicity take just ONE switch: When the (float) switch closes, the timer triggers, water is pumped for a period of time set by the potentiometer (11 to 110secs-ish) - almost immediately (after pumped water starts to fill the tank) the switch opens (indicating a 'full' tank again), however the pump will continue to fill the tank with water because the circuitry has now been triggered to keep the pump filling the tank.

Clear as mud or crystal?

Andy

 

[SkiFletch]

Crystal now

I would still make SURE to clean my float switches religiously. Because if one switch sticks up (snail, bubble, saltcreep, algae, etc), the circuit remains open and it will not topup. Over the course of a day, probably no big deal, but if you get lazy and/or go on a long trip, it may be easy for evap to drain the tank in such a failure condition. Worse still, if on vacation, it could evap to the point of a dry burned out pump. What would make the system absoloutely failsafe would be if powerhead rpms could be monitored, and if they skyrocketed (pump dry) the topoff comes on for said period of time I realize I'm chasing large quantities of unobtainium here, but hey, a guy can dream

Btw Andy, I know I said it before, but great job with this. Now all I have to do is translate it to US parts

 

[Underwurlde]

Cool. Do you want one of the PCBs?

Andy

 

[sophos9]

Last night saw the switches go in the tank, the water container in the cabinet and the pump wired in... With the sensors activated, I eagerly awaited the water to hit the tank and switch off!

One small thing I overlooked - the power of the pump...

You the 300lph was not powerful enough to push the water up the pipe so I grabbed a 600lph pump which also did not have the power!! It looks like I'm going to have to find a cheap peri pump to do this job - what an ass, well wanted it working last night!!

Arrghhh

 

[Underwurlde]

Where was the pump placed and what height differential are we talking about?

Should have been able to pump water IMO...

Andy

 

[sophos9]

pump was at the bottom of the stand in the water container, the height it needs to travel is 2m, ot got to about 1.2m and that was that...

Cheers mate

 

[Underwurlde]

Two METERS!!!

I'm 6ft1 and that's taller than me!

It's a fumction of the weight of water and therefore a function of the height (2M) and diameter of tubing.... So therefore either reduce the height or use smaller diameter tubing = less weight of water to pump = less work to do.

Therefore, to get it to work, reduce the diameter of the pipe?

Andy

 

[Fatty]

Therefore, to get it to work, reduce the diameter of the pipe?

Andy

Aha!, something I understand atlast, I think!?, changing the diameter of the pipe won't make a difference, normal pumps operate on 'head' of water so it doesn't matter how wide or narrow the pipe is if it won't pump up to that height it just won't. Changing the diameter will just mean it reaches the same height a bit quicker with increased flow rate.

Is the plan to get a final how to do diy thing on this auto top off, I am very interested, but wondering if it's going to be close to the price of the bought ones?? Apologies if you have already posted the 'full instructions', was finding following it all a bit taxing on the noggin!

Keep up the good work!

Cheers

 

[Underwurlde]

Aha!, something I understand atlast, I think!?, changing the diameter of the pipe won't make a difference, normal pumps operate on 'head' of water so it doesn't matter how wide or narrow the pipe is if it won't pump up to that height it just won't. Changing the diameter will just mean it reaches the same height a bit quicker with increased flow rate.

...are you sure? I'm no expert on pumps so I'll shut up now...

Is the plan to get a final how to do diy thing on this auto top off, I am very interested, but wondering if it's going to be close to the price of the bought ones??

Yes, this project needs finalising with regards a complete parts list. I was thinking the bit cost about £20 - I think Sophos actaully paid more than that in the end, closer to £30.... but I have yet to see his figures. Commercial ones, including delivery are closer to the £45 to £50 mark.

This design also has some safety features built in, but the price does NOT include a mains lead or float switches.... So at the end of the day I guess the price between this and commercially available ones will at the end of the day be pretty close.....

Such is life

Andy

 

[Fatty]

...are you sure? I'm no expert on pumps so I'll shut up now...

Yeh, it's the pressure that conventional pumps work against, and the pressure is purely a function of height of water. I do see how you think it might work because before I thought about it logically I too changed the diameter of the pipe down to an airline tube!! and guess what, .. it made no difference!

If you were to use a dosing peristaltic? pump, like the blood pumps, as they work by pushing the fluid thru a pipe by squeezing it I'd guess that they can achieve a higher head.

I'd just get a bigger pump, or move the resevoir higher

 

[sophos9]

Hi all, great conversation!

I used 3 different diameter pipes from normal airline through to 22mm, each time the water reached the same height just a different speeds (as fatty said)

Peri pumps are capable of pushing water silly height! Cannot move the reservoir higher, may get a higher pump but have no idea now what I would actually need so think I will have to get a peri...? Is there some equation on height, diameter and weight of material being pumped?

Cheers