I don't think I'll ever understand the obsession of people to power stuff off their USB port.

But who wouldn't want to flush their toilet via their laptop!?

There's an app for cr.... well never mind.

 

I don't think I'll ever understand the obsession of people to power stuff off their USB port. It has to be the worst idea to ever come down the pike, especially with reactive loads like a relay coil.

BTW, when you get this all working I think it would behoove you to have a failsafe backup to shut the fill pump off in case of float switch failure.

There is no obsession! Sometimes you want to control something via a computer and USB is a handy way of doing it?! I eventually want this to be unattended, so I will write an application that sets it off on an event timer.

I also monitor the temperature, amount of free ammonia and PH levels in my tank using the PC - so I would like to also be able to fire off a water change if the PH levels get too high or too low (and obviously I'd have a way of making sure it would only do a water change once every day).

I'm not being funny - but why bother to post on a forum in such a negative way and then offer no solutions to your reservations on this project.

And yes - I have a fail safe already built in to the empty pump system to prevent it from emptying the whole tank - I simply put the pump about 4 inches from the top! And I have been looking into a fail-safe for the inlet water in the shape of a float valve: http://bit.ly/I1G4kj

I'm not an idiot!

 

Could you provide a text explanation for that circuit?

because, As I see it...

1. I don't know how long your pulse is, but if you're expecting RL1 to latch, there's no provision for that.

2. during the brief time of the pulse, your pump & solenoid will be active, but they are in series which will give unpredictable results at best.

3. RL2 will latch, & keep your pump running (maybe) if the level is high (good there), but why not send the pulse straight to RL2? RL1 is pointless.

4. The low level switch will keep an open circuit for RL3 coil if the level is high, but if the level is low, it will connect both sides of RL3 together (electrically common) and RL3 will never switch.

5. Since RL3 never switches, RL4 never latches, and your tank never fills.

6. If RL3 were to switch, I think the rest of the circuit would work.

Hi,

Thanks for all these points - I will look into them and come back to you. There are a few good points there

Really quickly I'll answer my initial thoughts:

1. Pulse will be about a second or 2 - it doesn't really matter as long as the pulse is shorter than the time it takes the empty process to complete

2. I ballsed up the latch circuit there! I'll fix that - and I couldn't decide on series or parallel for the pump and solenoid - you've convinced me - parallel it is!

3. True - very true!

4. I got the switches drawn wrong (it was late in the day!) I'll correct that.

5. RL3 should switch... I'll fix the drawing

6. I think so too... I'll redraw the circuit with clearer explanations of how it should work and post it here asap

 

Here goes...

USB relay 2 will be switched on throughout - that is the "main" power switch.

To start the process, USB Relay 1 will be switched on for about 10 seconds and then off again... this is the trigger that will set RL1 to latch on causing the empty pump and the solenoid to switch on.

As the water level lowers, it will first switch SW3 on and then switch SW1 off. Once SW1 is off, it will break the latch circuit causing RL2 to switch on, which in turn will cause RL3 to latch on making the fill pump activate.

As the water level rises, SW3 will switch off turning RL2 off and then once the water hits the top, SW2 will switch off causing the latch circuit to break and switching off the fill pump.

Can anyone see any problems??

 

There is no obsession! Sometimes you want to control something via a computer and USB is a handy way of doing it?! I'm not an idiot!

No need to get yourself all out of joint over of my statements. I'm not questioning the wisdom of controlling hardware from your PC, that's a typical application of a PC. I've re-read this entire thread, to make sure I didn't miss it and I found no details regarding the box on your schematic marked PPUSB-RLY02, which I assumed are merely relays. If they are then that's where my issue is.

 

I know that's where your problem lies - but you offered no alternative... you just complained about it - that's where my problem lies.

I'm not interested in getting into a lengthy debate about it though - if you want more information on that little device, it's available here: http://bit.ly/HPXaqh

 

I know that's where your problem lies - but you offered no alternative... you just complained about it - that's where my problem lies.

I'm not interested in getting into a lengthy debate about it though - if you want more information on that little device, it's available here: http://bit.ly/HPXaqh

Complained about it? Not really. Questioning something vs complaining about it are hardly equivalent. This is the first time you've provided any information regarding that interface, which appears more than adequate for your application.

BTW, considering your extremely short fuse I'm looking forward to your first exchange with our senior member AudioGuru.

Someone please PM me when that happens. I really don't want to miss it.

 

I also monitor the temperature, amount of free ammonia and PH levels in my tank using the PC...

You should have mentioned that from the start. Using something like a LabJack or a DATAQ, you could collect all your data inputs and control a range of outputs all with one USB-connected device and your PC. Soooo much easier.

 

BTW, considering your extremely short fuse I'm looking forward to your first exchange with our senior member AudioGuru.

Someone please PM me when that happens. I really don't want to miss it.

You're probably right... I probably have a short fuse! (If only you knew me, you'd see how far wrong you are!). Please don't bother replying - it will only serve to prove that you are petty minded and desperate to have the last word.

I'm allowed the last word here - I started the thread!

Anyway...

I'd like to thank strantor for all the advice, along with the other guys who posted in this thread. I think I'm on the way to getting this sorted - I just needed a sounding board I think

I'll make a test circuit with minimum components and see if I can get it working... I'll try and post back my results with the final circuit diagram once it's all working.


Thanks

 

You should have mentioned that from the start. Using something like a LabJack or a DATAQ, you could collect all your data inputs and control a range of outputs all with one USB-connected device and your PC. Soooo much easier.

I'm using a Seneye. I've been talking to the dev's and they're hoping to make some sort of API so I can tap into the raw data from it... but it means I don't have to build my own circuit for it - why bother when someone's done the leg work already!

http://www.seneye.com/

 

Guys, guys...
Come on now...

I'm super busy right now (moving to a new house)
No time to provide useful input, but later on this evening I'll sit down and go over post #24 and get back to you.

 

I'm using a Seneye. I've been talking to the dev's and they're hoping to make some sort of API so I can tap into the raw data from it... but it means I don't have to build my own circuit for it - why bother when someone's done the leg work already!

http://www.seneye.com/

Hmmm, that device appears to only monitor (input) a few parameters and has no outputs that you could use to control relays and such. I thought maybe you were using something more versatile, like the other devices I noted. The Seneye probably wouldn't help much with your flushing project. Those other devices can control all sorts of outputs from your computer, programmed as you like.

 

Hmmm, that device appears to only monitor (input) a few parameters and has no outputs that you could use to control relays and such. I thought maybe you were using something more versatile, like the other devices I noted. The Seneye probably wouldn't help much with your flushing project. Those other devices can control all sorts of outputs from your computer, programmed as you like.

Yeh - it basically monitors my tank for me... and if there are problems it emails and sends me a text... What I was discussing with the developers was for them to ALSO send some sort of API command that I can use to fire off a water change.

I haven't got the time or patience to be inventing my own tank ph and amonia monitor - I'll leave that up to them! But you are right, with more time - it would be nicer to have it all coming from one handy USB device.

@strantor: Sorry - some things just spiral... it's over now! Anyway - I've attached the latest version of this project. I've added a bunch of indicators which will display what's going on... don't worry too much about them! I have also added 2 more switches - one is to start a cycle manually without needing the PC (SW4) and the other is to manually override the lights or auxilary device (SW5).

Hope it all makes sense

 

Then it wouldn't be automatic. The end goal is to have the outlet going into a drain and the inlet coming from some sort of hidden sump that fills itself with water and aquasafe chemicals... but that's another part of this project!

Also - I didn't mention that there will be a solenoid valve on the outlet that will be connected to the same power source as the outlet pump. That way, once the outlet pump turns on - the valve will open, when power is removed - the valve will shut preventing accidental syphoning.

@strantor - I'm not 100% sure on the ladder logic! (at least I'm honest!)

Can you draw it in a standard schematic circuit diagram at all? Many thanks everyone

after years of splashing around in aquaria, I settled on siphon draw filtration. I bore a port into the side of the filter canisters to allow high flow to run off to drain (sourced from below filter media to prevent fry going down and rising media that could obstruct the port). My original conditioning tank was level and continously siphoned to main tank as fresh was added. I did not attempt to adjust chemicals, only to let it 'age'. A line from main filter returned some flow back to the conditioning tank. My last setup had the conditioning tank flowing into a live breader tank (guppies), then into the angel rearing tank. No pumps, no hassle, just a good air stone in the conditioning tank.

No reason you couldn't adjust chemicals in the conditioning tank, other than overdose.

My twenty some odd tanks are stacked in one corner of the basement and the wife is pressuring me to start getting rid of them, but I'm thinking a couple more brood of angels would be exciting.

 

@blindtrevor - you really can't put things in series man, especially lamps. Lamps are high value current limiting resistors. Your motors are probably supposed to be drawing several amps; you put a lamp in series with it, and now it's only going to get a few milliamps. Putting a lamp in series with a relay coil is going to cause the coils strength to be weak, which is going to cause your contacts to flop around all over, arcing, & burning of the contacts. Other than that, it looks like it should work.

P.S. I highly recommend you familiarize yourself with relay ladder logic diagrams. They really are the simplest, most intuitive way to draw a relay circuit. Your first drawing took me probably 10 minutes to examine; this latest one took only 5 because I was already familiar with most of it. If it had been in ladder form, I could have cut the time down to a few seconds. Actually, this thread is one of 3 in recent memory that has prompted me to make a little "Relay Ladder Logic Diagrams for Dummies" thread. But you can check out AAC's e-book on it for now: http://www.allaboutcircuits.com/vol_4/chpt_6/1.html

 

Yeh - I know... sorry, I should have been clearer

When I said, don't worry about the lamps, I meant because I had thrown them in roughly where they needed to go - they haven't been connected properly yet - I had only just started adding them in

I got into a conversation with someone last night who seems to think the relay won't latch because of the voltage drop across the relay while the motor and solenoid are on... I think he's wrong - he's gone away to redesign the circuit!

I'm interested to hear your and other peoples views on that?

 

I got into a conversation with someone last night who seems to think the relay won't latch because of the voltage drop across the relay while the motor and solenoid are on... I think he's wrong - he's gone away to redesign the circuit!

I'm interested to hear your and other peoples views on that?

It will latch. These holding circuits have been used in conjunction with motors since relays & motors existed. If your relay coil was in series with the motor, then you would have a problem, but it's not. How does he propose to redesign the circuit in such a way that the "theoretical" dropping out of the relay will not happen? Any way he does it will require a relay to latch at the same time the motor is running.

 

I'll beat this dead horse 1 more time...

I hope you don't mind, but I've taken the liberty of converting your schematic to Ladder form. In doing so, I uncovered 2 departures from convention & one more redundant relay. I did not catch these errors in your schematic because the format is not conducive to my understanding.

You'll see I've circled SW1 & SW2 - these 2 float switches are positioned between the relay coil and neutral. This is bad form. The convention is to always have one side of the relay coil connected to neutral. This is especially important in DC circuits, as the collapsing field of the relay coil will arc across upstream contacts and burn them out prematurely.

I've drawn a line between RL2 coil and RL2 N.O. contact; as you can see, RL2 is not needed. You could simply go through RL1 N.C. contact, through SW3, and then to RL3 coil.

BTW, Do you mind if I use this thread as part of my tutorial?

 

Oh yeah because everyone understands relay/ladder logic diagrams..

Well they should; it's about the most elementary way to draw it short of filling up a page full of relay symbols and playing connect the dots.

@strantor - I'm not 100% sure on the ladder logic! (at least I'm honest!)
Can you draw it in a standard schematic circuit diagram at all? Many thanks everyone

The comment by wayneh not withstanding, (it's true) I find this funny! It certainly gets your ladder vs conventional schematic point across vividly.

I'll beat this dead horse 1 more time...

... Do you mind if I use this thread as part of my tutorial?

http://forum.allaboutcircuits.com/showthread.php?t=69884

 

http://forum.allaboutcircuits.com/showthread.php?t=69884

Oh - sorry... feel free!!

I've had some stuff happen that's taken my mind away from this project for a short while... but I'll be back on it soon enough!