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I have modified your original drawing to include the items in red, I have moved the power switch, fixed the 240VAC relay contacts, added labels. You can get float switches that have mechanical hysteresis via a sliding float. Just some suggestions, but thought that I would point out some easy fixes. You need to add resistors for the LEDs shown as diodes "POWER ON", "TANK SW" and "PUMP ON". I got lazy drawing the LEDs.
Let me know if you have questions.
Hope this helps...
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Don't forget the current limiting resistors for those diodes which I assume must be LEDs.
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I wonder what the simplest solution to get the Tank and Sump float switches to have LEDs independently is.
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I wonder what the simplest solution to get the Tank and Sump float switches to have LEDs independently is.
Could do what household switches do: put the LED and resistor in parallel with the float switch. When the switch is closed the voltage across the LED is zero so it is out. When the switch opens the voltage appears across the LED and it lights up. -
I wonder what the simplest solution to get the Tank and Sump float switches to have LEDs independently is.
Can you use float switches with opposite polarity (so they would conduct when the water is at the level you don't want)? -
The problem with that is that his relay probably works with 20mA (or at least get into "weird" state). He would have to use low current LEDs.I wonder what the simplest solution to get the Tank and Sump float switches to have LEDs independently is.
Could do what household switches do: put the LED and resistor in parallel with the float switch. When the switch is closed the voltage across the LED is zero so it is out. When the switch opens the voltage appears across the LED and it lights up. -
That's an easy fix if you don't mind wasting a bit of power - just put a suitable resistor across the relay coil to keep it well below its minimum operating voltage when passing the LED current. If you want to get cute and waste less power when the pump's running, use a JFET selected for an Idss > LED If, as a current sink.
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Since you are using normaly closed switches, you will have to first invert their signal for the LEDs. You could do something like this:
http://tinyurl.com/y8jx99uo
(100k and 100n are for the reasonable simulation, they would have to be much larger, something like 1M/470u)
Or you could improve the slow switch on wit the LED (if you have higher voltage than what you need for relay):
http://tinyurl.com/y8wwwpmc
On the other hand, it would be much easier with the reversed polarity floaters (when the water level reaches max, they conduct):
http://tinyurl.com/ydcm9lj3
(the 100k should be something like 1M and 100n at least 100u, which will give you delay of about 2 minutes)
To the PCB and what tautech wrote, I don't think it's an awful design, far from it for a first timer.
Things that you should always consider when making PCB:- What is the manufacturing method. Are you gonna use company (f.e. I use AllPCB even for my prototypes and with something that I am able to do within few hours myself. Just because of the lazynes and the quality vs. price/time spend)
- Are you going to solder it by hand or do you have something better.
- How are you gonna mount that board (you are missing mounting holes, which is good to have even if you don't use them later)
If you are making single sided PCB and you are planning to solder it by hand, you need bigger angular rings (around pins of each device). Those tiny ones are almost impossible to drill through and then solder without ripping them of the board. Drill sizes should be just enough to put those components thru, It will be hard to solder if you have too much space around the leg.
On the other hand, if the PCB is going to be double sided (even if you don't have anything but the pads on the other side), you can get away with tiny holes - because the solder is going to fill the space inside the pad. In this case, it's good to make those holes a bit bigger in diameter so you have space between the leg and plated hole.
If you would to use SMDs, there is a big difference in the footprints for different methods of assembly. -
To the PCB and what tautech wrote, I don't think it's an awful design, far from it for a first timer.
Well done for seeing through my comments and adding further good advice.
Things that you should always consider when making PCB:- What is the manufacturing method. Are you gonna use company (f.e. I use AllPCB even for my prototypes and with something that I am able to do within few hours myself. Just because of the lazynes and the quality vs. price/time spend)
- Are you going to solder it by hand or do you have something better.
- How are you gonna mount that board (you are missing mounting holes, which is good to have even if you don't use them later)
If you are making single sided PCB and you are planning to solder it by hand, you need bigger angular rings (around pins of each device). Those tiny ones are almost impossible to drill through and then solder without ripping them of the board. Drill sizes should be just enough to put those components thru, It will be hard to solder if you have too much space around the leg.
On the other hand, if the PCB is going to be double sided (even if you don't have anything but the pads on the other side), you can get away with tiny holes - because the solder is going to fill the space inside the pad. In this case, it's good to make those holes a bit bigger in diameter so you have space between the leg and plated hole.
If you would to use SMDs, there is a big difference in the footprints for different methods of assembly.
I never called the design 'awful', instead saying that my mentor would do so and I can tell you that really makes you focus on creating a better layout and taking more attention to detail. I hope the OP can see this too.
Doing good layouts is a real craft and I learnt a lot from studying old PCB's in my junk pile to the point now I can look at a board and quickly know if the CAD artist has any pride in their work.
One of the most challenging to do when you start is a dense single side board where the routing options can be very limited so much time and experimentation must be spent on placement and orientation otherwise your board looks like it was done by the other side 'jumper king'!
Good boards take time and lots of time, but the satisfaction of knowing it can't be bettered is worth it.
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The problem with that is that his relay probably works with 20mA (or at least get into "weird" state). He would have to use low current LEDs.
Every red LED in my junkbox puts out a significant (like very usable for an indicator) amount of light at < 1mA. The greens and yellows, not so much.
A red or blue Ultrabright at <1mA is well and truly enough for anything not in direct sunlight. -
I never called the design 'awful', instead saying that my mentor would do so and I can tell you that really makes you focus on creating a better layout and taking more attention to detail. I hope the OP can see this too.
It's quite ok. I have thick skin, and of course my noob PCB is going to be flawed. I really only designed it to see if I even could design a potentially functioning circuit board. I have no intention of sending any design off for building without being 100% satisfied that a prototype would even work. In fact, if I ever get that far I'll be sure to post a picture here for intense scrutiny.Cool simulations
1. Holy moley I was looking for a circuit simulator just like this to play around with. I trawled all sorts of places and couldn't find anything that wasn't behind a paywall or otherwise crazily complex.
On the other hand, it would be much easier with the reversed polarity floaters (when the water level reaches max, they conduct):
http://tinyurl.com/ydcm9lj3
(the 100k should be something like 1M and 100n at least 100u, which will give you delay of about 2 minutes)
2. Hysteresis isn't a bad idea, and a slow turn on would actually reduce the relatively rapid on/off switching problem quite a bit. I really should have been more clear in stating that a latched error state is better since if it happens, then manual input is going to be needed anyway (ie. add more water or clear the drain blockage).
I can't understate the beauty of that design though. When I get my breadboard I'll get some mosfets and try out that 3rd design.
https://tinyurl.com/yd7q87br I added some normal state indicator LEDs (green). If I were to use superbrights (which is what I have): Vf 3-3.2, If 20mA, that would require a lower value resistor - but would that interfere with the mosfet at all?
It's also entirely possible to reverse the float switches into a normally open state. One of them would be a big pain in the ass to change, but is entirely doable.Why not use a double pole relay and put one pole in series with your float switches. Put a button in parallel with the whole switch chain. That will pull in and stay in when you press the button, and if either float switch opens up the relay drops out and stays dropped out. No transisors, no semiconductors. You could wire it such that the contact that drops out powers the led when the pump is inactive.
I really like this idea because it's simple and therefore robust. I think if that can be integrated with Mr Kev's design #3 that would satisfy all the requirements. One question - is it safe to be switching AC240V on one pole, and 9V on the other? That seems uncomfortably close in proximity. I suppose a second relay could run from the DPST though.Things that you should always consider when making PCB:
I'm hoping that I get to a point where I can actually implement this advice. Particularly, adding mounting holes is a legitimately good idea- Sage PCB advice
- Sage PCB advice
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It's quite ok. I have thick skin, and of course my noob PCB is going to be flawed. I really only designed it to see if I even could design a potentially functioning circuit board. I have no intention of sending any design off for building without being 100% satisfied that a prototype would even work. In fact, if I ever get that far I'll be sure to post a picture here for intense scrutiny.
Hey, I've done my first board 22 years ago, when I was 8yo. And I've done it by physicaly sticking resistors throught the squared paper, drawing the paths with pencil and then redrawing the design on copper board with fix and etching it in ferous chloride. The thing is tho, that you make the most progrees only after you try. And with every board, you get to know what is important in the desing.1. Holy moley I was looking for a circuit simulator just like this to play around with. I trawled all sorts of places and couldn't find anything that wasn't behind a paywall or otherwise crazily complex.
ad 1. It's not anything perfect, but it's great for first design idea.
2. Hysteresis isn't a bad idea, and a slow turn on would actually reduce the relatively rapid on/off switching problem quite a bit. I really should have been more clear in stating that a latched error state is better since if it happens, then manual input is going to be needed anyway (ie. add more water or clear the drain blockage).
...I added some normal state indicator LEDs (green). If I were to use superbrights (which is what I have): Vf 3-3.2, If 20mA, that would require a lower value resistor - but would that interfere with the mosfet at all?
ad 2. Then you want a R-S flip flop (or mono stable flip flop). You can do it with that relay (as someone else mentioned it before), or even with those transistors, since it's really easy. Also, if you are OK with having only "floater OK"signalization, it could be done something like this: http://tinyurl.com/yd9hqhqn
Hitting the "restart" pushbutton will switch on pump, and if any floater gets open, it will switch off and stay switched off untill you hit the "restart" button again (it's held by small current throught relay and third diode).I really like this idea because it's simple and therefore robust. I think if that can be integrated with Mr Kev's design #3 that would satisfy all the requirements. One question - is it safe to be switching AC240V on one pole, and 9V on the other? That seems uncomfortably close in proximity. I suppose a second relay could run from the DPST though.
If it's safe, that deppends on the construction of the relay and PCB. On the other hand, you should always use DPST relay to switch 230/240VAC and switch both sides (L and N). You never know where the L actually is and you could be switching N, making the pump connected to the mains voltage even if it's switched off. It's in fact required by the law in most states (deffinitely here in EU). -
I really wouldn't want to have mains on one pole of an ordinary DPDT relay and low voltage on the other. OTOH that's no problem if you are using a proper contactor - the auxiliary contacts have *PLENTY* of insulation between them and the main contacts, and are intended for control circuit use. However contactors are big, expensive, power-hungry and noisy (an almighty thump when they open or close isn't unusual), so your idea of an auxiliary holding relay with its coil in parallel with the main one is probably preferable.
Personally, I'd design the relay circuit to latch on when a fault occurs, and be reset by breaking the coil power rather than manually latching it and a fault causing it to drop out, as otherwise any brief interruption of the mains supply will cause the circulation pump to stop untill manually reset. Its easy enough to rearrange - put N.O. sensing switches in parallel to connect power to the coil when a fault occurs, with a N.O. auxillary contact in parallel with them all to latch the coil on, then use a N.C. contac pair to interrupt the load circuit.
An alternative would be to do the latching in silicon. If you use a thyristor (or SCR) with the fault conditions triggering it, it could hold the relay coil ON, so that the pump wired via a N.C. contact pair is held off until you clear the fault by removing power from the control circuit. Cathode to ground, Anode to relay coil, and fault switches can either be N.C., (multiple in series) shorting the Gate to the Cathode, with a pullup resistor to +V to trigger it when they open, or you can put a pulldown resitor from Gate to Cathode to prevent false triggering and connect a pullup resistor via a N.O. switch (multiple in parallel) to trigger it. Use multiple thyristors, one for each sensor switch, and add some steering diodes and you could even implement a latching fault indicator LED - they all operate the same relay, but only the one that was triggered lights its LED.
Another thing to consider would be to add a SMS dialler so your tank can text you if something fails. A typical SMS dialler requires 12V power, a paid-up SIM card and has several inputs that cause it to send different messages when triggered. However at that point its probably worth making the whole system Arduino based using a SMS shield so you can easily add alerts for over or under temperature, or aeration pump failure (and cut in a backup heater or pump).
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2. Then you want a R-S flip flop (or mono stable flip flop). You can do it with that relay (as someone else mentioned it before), or even with those transistors, since it's really easy. Also, if you are OK with having only "floater OK"signalization, it could be done something like this: http://tinyurl.com/yd9hqhqn
Hitting the "restart" pushbutton will switch on pump, and if any floater gets open, it will switch off and stay switched off untill you hit the "restart" button again (it's held by small current throught relay and third diode).
Ha! That's perfect. I started this idea with an R-S monostable latch in mind, but I couldn't work out how to implement it into the main design.
I tweaked it a little bit:
http://tinyurl.com/y7oc33a8
I tried putting in a couple of transistors that would switch the green LED to red (I have a couple of two state LEDs), but I just ended up making a bypass to the float switches. I think I'll stick to the Mr Kev Mk3B and just be done with it :p
I think I'll get started designing this and try it out on a breadboard. I'll have to get some mosfets though. I'll post an update when I've made a prototype.
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Hey, that's a great idea, really! I wanna see someone do it! I love aquariums that have been innovated by people who own them, that shows your interest in the success of your work! The aquarium pump controller shouldn't be plain and uninteresting. My friend has an amazing aquarium that was decorated all by himself! Even when appeared a problem with a bristle worm, he solved it with fashion! I think it's great and wish you luck!
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The relay wired as shown will never close the load circuit. You need to attach to the armature leg in the center.