Control 5 inputs through a relay

Projects General Guidance
1

Hey guys, hope you're all OK.

I was tasked with a proof of concept of a DIY temp. control unit and I cannot figure this out. I was tasked at keeping a volume of water at 37 degrees C in a flow circuit. The water is being pumped from a sump up into a header tank which contains a weir/overflow to send the water back down into the sump via gravity. Total height of no more than 1m.

I have a kettle element which was connected to a mains switch via a 3 pinned computer power lead, I've wired to an extension chord which is wired to the relay, something like this (LINK REMOVED - AC WALL MAINS -> PLUG -> EXTENSION SOCKET -> RELAY -> ARDUINO). I apologise for not having any photos, I took everything apart in my frustrations at an earlier time.

Please refer to my crude depiction below re electric circuit and what im trying to create:

crude depiction
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So what I am attempting to achieve is to have the arduino read temperature of the water and turn on the heating if below set point and turn on cooling circulation to fan/peltier if too hot

My issue is I do not know how to power the peltier and the fan. Do I use a 8.3A power source at 12V or 24V in form of an adapter like a laptop charger or opt for one of those 'LED drivers'

I understand I will need to probably switch to a 8 channel relay but if all 5 components are connected to mains then I may as well hook up a 5 gang extension to a wire and somehow wire that to the relay. Something tells me its not going to be that simple however.

I am really stuck on how to power the Peltier and the fan, I think switching the relay is the quickest and easiest way of doing this in my limited time. I wanted to add some push buttons but If i go for 5 channels required i think i may quickly run out of enough input pins.

I do also want to wire some sort of push button thing to the arduino so it can override the setting of low or high to relay

I hope this makes sense and I am open to any and all ideas. I am a bit desperate at the moment and if there are differnet ways to do this I am more than happy to consider but please do realise i need the quickest way possible. I have a day or two in which to order some extra parts if necessary but nothing after that. I appreciate any suggestions you may have and even reasons as to why not to do it this way would be very much appreciated.

I hope my discombobulated thoughts made enough sense for you to figure out what I am attempting here, if not, please ask and I will do my best to explain.

I appreciate you taking the time out to read this and providing me with some much needed guidance.

Stay safe all and thank you again,
Harry

2

Please refer to parts below which I have been given:

Arduino Uno Rev 3
4 channel relay module
12v dc 100w cpu cooling fan
24v dc 200w 13A peltier module
2 x mains powered water pumps

3

I am not worried about the mains connected appliances as I'm confident i can interface them

Please see absolutely rubbish diagram of what I am attempting to demonstrate

crude2
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My apologies for the tripe post, I am link and attachment limited

4

Is the fan to cool the heat sink on your Peltier device? I sure hope so! You can just leave it on full time.

5

There’s a lot of detail missing in your proposal…
As noted,above, you’re switching quite a lot of power, and planning is needed for the power supplies and cooling.

You don’t indicate any relationship between the controller and anything other than the relays…. this suggests it’s simply switching the relays on in some timed sequence, or are there sensors providing data to the controller?

In many block diagrams, the controller is shown in the ‘middle’, with inputs on the left, and controlled outputs on the right. Power supplies typically run across the top and bottom to link the related components.

6

Yes, serving no other function but to dissipate heat from the peltier

7

A Type K Narrow Immersion Temperature Probe connected to a MAX6675 module that is giving me temperature readings

I'm sorry about the block diagram if it caused any confusion, i just put it together in order to illustrate what it is I am trying to do. The two pumps and the heater element can be connected to a socket thats wired to mains with the relay in between the socket and the arduino, like this

What I'm trying to get is for the arduino to op

222
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en relay when temp is below 37 to turn heater on, and when above to turn heater off and turn pump / fan / peltier on to remove heat from water, and continuously cycle as necessary.

I only need for it to work for like a 10 minute demonstration, it will not be functional and actually doing anything aside from doing its intended task for a brief moment in time. My challenge is just to make sure I dont fry anything before then.

Do you think it would be best to get one of those power supplies advertised as LED Drivers and connect that to mains and in series with the components relay connection...would that work?

I'm struggling to find a 200W 24V power adapter...i was thinking if i could find a rated adapter then all I would need to do is connect the comoponent in series and just plug it into the extra socket between wall outlet and relay and just flick that on or off...but i cannot find a suitable on

The current rating on peltier at max temp differential is 13A, would the fan be taing 8.3A or could that have higher current draw as well? for peltier 24/200 = 8.3A

they would both draw 8.3.A but i read online that some components have higher current draws at start up...
this may be a stupid question but how exactly would the component regulate the current?

If I had a 10A 24V (250W i think) and connected it to peltier, wouldnt it have to have improved heat removal in order to draw that current? if 250W of heat is not being removed from peltier can it draw that amount of current?

or could i use a 12v 100W 5A power adapter to power the fan?

8

hmmm i see what you're saying here.

If my fan is only removing 100W of heat, will the peltier still draw the max current? Would I still have to ensure the peltier is powered by a 13A 24VDC supply?

tempdata

I can just keep that and the fan on when the rest of the rail is switched on and just control the pump feeding the water through the aluminum block on the cold side of the peltier...

that makes a lot of sense. Thank you

9

That must be one hell of a fan, 12 V, 100 Watt. Do You intend to blow the hole installation away? It's surprising how little fan blow cooling needs. If the Peltier reaches too high temperatures, switch it off. Cooling must be possible to do with a lot less powerful fan. How to power it? Use 12 volt and calculate what the current adds to the other 12 volt consuming parts.

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10

Since the Peltier device consists of many metallic diodes in SERIES. the voltage must the be the rated voltage. It will draw whatever current it is rated at. So will produce the heat from the diode junctions plus the small amount of heat being moved from one side to the other.

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11

I'm just trying to make it work with what I have. I have a few days to downsize on components if needed but my window of time is very small.

Please elaborate on what you mean calculate what current adds to the other 12V consuming parts? Does it matter if they are being powered from separate sources and not sharing a power supply? Everything will be connected to its own mains outlet, especially if I use a power adapter

12

Thank you.

So it will have to be a 13A supply or can i get away with a 9A supply? ...13A 200w 24VDC power supplies seem to be used on medical equipment and are far far outside of the price I am willing to pay +£60...

Would I be able to power the fan with this?

AC/DC 100W 12V DC 8.5A Enclosed Switchmode Power Supply -

13

And would I be able to power the peltier with this?
AC/DC Enclosed Power Supply (PSU), 240 to 370VDC, ITE, 1 Outputs, 211.2 W, 24 V, 8.8 A

Appreciate your responses guys, my apologies again, and thank you for bearing with me

14

That is bad. Why not asking forum in good time? I'll answer as often as I see a post from You but, no, I don't take on any time issues.

You use quite a number of devices. All devices using the same voltage can favourably be using the same power supply.
I've not invented the power situation for Your project.

Elaborating.... Often different voltages are needed. Group them together and use one power supply for each voltage. Sum up the current need for each voltage. Then buy/use the power supplies needed for each voltage.
Yes, good You have mains "behind Your back".

Eehh... Are the parts physically separated from each other?

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15

As mentioned, the devices will pull the current they need. You must ensure that the power supply for each is the right voltage and can provide enough current and a bit more. You do not need to find a supply that is exactly 13A.

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16

You posted during the time I was writing my previous reply.
Just compare the current needed by the load and use a supply having that capacity.

Your first post has got "flagged" and info is hidden. Fasten the seatbelts....

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17

I completely understand this and I am in acknowledgement of my moronicity (?) :joy:

The devices I have been given are not rated at same voltage, if they were I understand I could have powered them from a single source, calculated the total current draw for totaal circuit from each component and chosen appropriately. I no longer have that luxury.

60W, AC 100-240V water pump
4W AC 220-240V water pump
1.2kW AC 240V kettle element

200W DC 24V Peltier
100W DC 12V fan

On top need to supply 5v to arduino and 9v to relay also... do you see my predicament? I am nowhere near well versed enough to be designing the step up / down transformer circuits for each component, and given the time I have and the stuff I have to achieve it with, this is the only way I can see how

And yes, they are separe parts, im not sure what you mean by that? The only thing that would be connecting them is the single extension socket they are plugged into and the connections at the relay...but im not entirely sure how i would wire this

18

I'm not sure what happened here, but I was asking if I would be able to power the 100w 12V fan with AC/DC 100W 12V DC 8.5A Enclosed Switchmode Power Supply

and would I be able to power the 200W 24V DC 13A peltier with AC/DC Enclosed Power Supply (PSU), 240 to 370VDC, ITE, 1 Outputs, 211.2 W, 24 V, 8.8 A

19

Does that statement seem logical to you? Do you see the difference in current required vs.current supplied?

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20

What's the voltage of Your mains?
Something is gone wrong so I can't read the 3-4 first posts telling the voltages of things, the pumps..

It's late here...... If two loads are situated close to each other sum up the need of power and use one supply. If the loads are far apart, use 2 supplies.

There's too much posting and hard to bring all info together...