Temperature regulation

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi I am new on this forum, and also when it comes to electronics and microprocessors.

I'm on to a project, trying to build a temperature regulation system in my sailboat, where I will use an arduino (pro mini), 1-wire temperature sensors (DS18B20), and some motor driver (L298).
The Arduino will control (PID, PWM) six 12v DC motors (fans) that will blow out heated air, from a heat exchanger, when needed.

Digging in this forum have given me a clue about how to use the the L298, but maybe some one can help me out before i start to fry components.

Wiring:
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  • Is it ok to use two by pass diodes (they can only handle 1A each), ore is one enough?

  • Ok to connect IN1 and IN2 directly to 5V and GND?

-If I want to limit the current (short circuit protection) and put a resistor between GND and "1", how can I hock this up to a I/O pin on the arduino when its connected to the 12v, and not to the 5v. Transistor?

Grateful fore all help I can get.

Happy new year!!!

2

And here comes the wiring:

http://www.geting.se/viewimage/image/278966-Bilder_002.GIF

3

...then you can use a simple transistor.

True... and less expensive than a relay, but not by much. If you want to "skip" one learning chore for the moment, a relay is an easier-to-understand (and do right) answer. Just be sure to include The Diode.

See...

... for The Diode.

Alternatively, a middle ground:

Opto-isoloators...

4

Tanks for such a quick response.

Richard, even whit my limited knowledge I must say that it make sense.... I will search on this forum to find out how to do it with a transistor in stead.

Unfortunately the relay will not do the job since I want to control the speed of the motors (PWM). How ever I have plans to drive a 12v circulation pump for the water system, and will use this setup.

http://www.geting.se/viewimage/image/279082-Bilder.jpg

Will it Work?

5

Thanks again Richard.

Done some research about controlling the DC motors, and have learned a bite about Optokoplers, Darlington transistors...

Since I already have ordered the L298, and figured out how they works, maybe I will leave the transistor controlling to another project. And go for the L298, even though I not using their full functionality.

Will it be ok to wiring them up like this?
http://www.geting.se/viewimage/image/278966-Bilder_002.GIF

The current throw L298 will be 1.5A, will I need a heat sink, not to burn them up?

6

Can't understand why I'm overloading the L298, it should withstand 2A? Or could it be that the start up current can be much higher?

Never the same... Let's have a further lock at the transistor...
Take this for example:
https://www1.elfa.se/data1/wwwroot/assets/datasheets/rcSTM_Leistungstransistor-BD241C_EN.pdf

Doesn't it only has a gain of 25?

Isn't it so that the arduino maximum can deliver 30mA on one pin?
And if I need 4A (guessing) start up current, I would need a gain of at least 4/0.03= 130?
Doesn't I need a darlington to fix this?

7

I looked for the TIP102 at a store nearby (https://www.elfa.se). Unfortunately they didn't have it, but they have TIP120. Will it work as well?

Wiring it like this:
http://www.geting.se/viewimage/image/279303-Bilder_003.jpg

The diodes for the back EMC, and the capacitor to cut down noise??

8

Sorry, 'back EMF', I meant.

9

Nice... can't wait to hock it up and test it.

I must agree, a much better design for this purpose.

Thank you.