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We are building a greenhouse box for strawberry plant. We need to control the humidity and temperature inside the box. We need to maintain in range of 23 - 18 degree Celcius and humidity in range of 68 - 73 %. So we arrange the peltier in parallel and also the fan in parallel. We have a voltage supply of 12 V 60 A. To make the pelteir run efficiently without any problem. What type of resistor should we use to make the peltier to take in range of 4 - 6 A, which mean to protect the peltier and the fan we need to choose a resistor which is suitable for specific current take in. We have 9 peltier and 18 fans. So we need to supply 12 V 4-6 A to every peltier and as for the fan we need to supply 12 V and 600 mA for every fan. So the question is if the overall current take in is about 57 A, what should we do with the excess current of 3 A? is there any possibility of burning or short? What resistor should we use? And what type of wiring cable size should we use to distribute the voltage and current to pcb board with 8 V strips?

Item specification Peltier (40 mm x 40 mm) 12 V 60 W Intel cooling Fan 12 V 600 mA Voltage supply 12 V 60 A

Wire size Used : For peltier Awg 24 For Fan (we use wiring that is suitable for electronic stuff example like raspberry pi or arduino)

Component connected to RPI 3: DHT22 x 2 Soil Moisture x 4 Relay Board v1.0 5V 2-channel relay board 7 inch official raspberry pi touchscreen

Purpose for Final Year Project

winny
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EIT17515B
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  • The guy was called *Peltier*, not *Peltier*! And it's a *Peltier element*, not a *peltier* (you're using a component named after the effect, named after the scientist, not the scientist himself, in your devices). – Marcus Müller Jun 25 '18 at 06:51
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    Also, draw a circuit of what you have, this is all very confusing. – Marcus Müller Jun 25 '18 at 06:53
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    @MarcusMüller "Peltier, not Peltier!" Read it five times. Every letter is the same. Typo? – winny Jun 25 '18 at 08:17
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    So much hand waving, so little schematic! – Olin Lathrop Jun 25 '18 at 11:32
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    @winny aaargh. I fixed the typo in the title. Then I fixed the typo in the "correct your typos in the text!" comment. Which is kind of ... counter-productive, isn't it? – Marcus Müller Jun 25 '18 at 12:33
  • @MarcusMüller Indeed. Just like scoring a goal at the last minute... – winny Jun 25 '18 at 14:06
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    Possible duplicate of [Choosing power supply, how to get the voltage and current ratings?](https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings) – winny Jun 25 '18 at 14:07
  • @winny Marcus has a spell checker built in. – Dmitry Grigoryev Jun 26 '18 at 06:39

2 Answers2

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I'm not sure whether I understand you question or not. You have a 12 V supply and components which require also 12 V, I don't think you will need any resistors.

We have a voltage supply of 12 V 60 A.

Keep in mind that it is a voltage source you are using, which has the intention of keeping its output voltage the same, no matter what current you try to get from it. The 60 A then should be the maximum current it can supply. It will not always give 12 V and 60 A at the same time. For example, if you would only connect a 1 Ohm resistor, the voltage across the resistor would be 12 V and the current trough it also 12 A (Ohm's Law). In order for the current to be 60 A the voltage across the resistor then should be 60 V.

Marcus Müller
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Robert
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I would recommend measuring the temperature of your peltier devices if your unsure about overheating. There's no harm in drawing 60A; so long as the cabling to your peltiers can handle the current demands and your peltiers manage the heat on the hot side.

I would advise on using 0.5mm CSA cabling or in AWG 18-20 would be good for handling 6A at low voltage.

TestDeviant
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