Connecting DC Air Compressor to Arduino

Hi there! I need to connect a DC air compressor to Arduino. I thought I'd be required to use a TIP122 transistor, which is specifically designed for DC motors. I've used the transistor before with motors, but it is pretty expensive. DC motors can fry the Arduino when it spins down, so that is why it requires the transistor, but what about the compressor? Would it work without the part?

you need to post a link to the air compressor.

only by seeing the data sheet can we begin to guess.

also, the TIP122, while good, is not as good as using a MOSFET, especially for higher loads

you statement that the transistor is needed because the motor spinning down can fry the Arduino is incorrect.

the Arduino would fry if you tried to power the motor directly because it is not designed to provide power, only signals.

I believe that what are thinking about is that when the motor is spinning down, it is a generator and will destroy any electronics on the line. that, or when power is removed from a motor, the magnetic fields in the coils collapse and generate a very high voltage EMF pulse, capable of destroying all electronics in the circuit.

to that, we laugh - HA ! - and use a 10 cent diode and protect everything.

That reminds me of a quote, from a game:
...and how we laughed and laughed...
except I wasn't laughing.

I couldn't find my Cartrend 18-BAR air compressor's designated datasheet. Instead, I found one that is exactly the same, both in specs and in appearence.
It has 18 BARs, it uses 12 volts, and it uses cigarette connection (I cut that plug, though).

Thanks for correcting my DC motor theory, and for the diode hint, but I would rather use a nice, small brick TIP122 transistor to gain an esthetical bonus.

I would assume that you can find the maximum design amp for an automobile power port. there has to be a rating.

all you need to do is make sure the power plug you make with your transistor has a heat sink large enough to handle the heat from a sustained operation.

inflating a tire or two might not get it too hot.

Since it appears you discharged the recommendation of the MOSFET out of hand, I would suggest you calculate the power for your air compressor. I believe that 10 amps would be maximum.
once you calculate the power passing through the TIP122, you can determine the heat being generated in the TIP122 and how many watt of heat you will have.

At 75 cents, I do not see a TIP122 as expensive and at $2.00 I do not see the correct device for the project should be rejected without consideration.

dave-in-nj:
you need to post a link to the air compressor.

only by seeing the data sheet can we begin to guess.

Yes, we need to know what size motor we are talking about.

Bulkduino:
I couldn't find my Cartrend 18-BAR air compressor's designated datasheet. Instead, I found one that is exactly the same, both in specs and in appearance.

You have found a datasheet for a similar model, but you still haven't let us in on the secret.
Could you post a link to the datasheet you have found, please?

Well, the tip122 is only rated 5A continuous and it's saturation voltage
at that is 4v - so it's dissipating 20W and so will need a VERY juicy heatsink
and it will only supply 8v to your compressor.

So I agree strongly with others that a modern MOSFET would be a
much better idea. IR, ST etc all make good ones.

regards

Allan.

JohnLincoln:
Yes, we need to know what size motor we are talking about.

the auto manufactueres rate the cigarette plug / outlet at 12v and 10 amps.

ergo, we can determine that the motor is not greater than 12v and 10 amps.

using that as the starting guessing point,....

Hi,
How often do you want to turn the compressor ON and OFF?

Cigarette or DC POWER OUTLETs that they are now called are rated at 120W, 12V 10A.

Thanks… Tom… :slight_smile:

dave-in-nj:
ergo, we can determine that the motor is not greater than 12v and 10 amps.

Don't bet on it!

Stall current could easily be 10 Amps.

Operation of these from a 4 Amp battery charger causes the cut-out to cycle when they get up to about 30 PSI.

Paul__B:
Don't bet on it!

Stall current could easily be 10 Amps.

Operation of these from a 4 Amp battery charger causes the cut-out to cycle when they get up to about 30 PSI.

and that is why the next line was
.....using that as the starting guessing point,....

a simple FET that is the same size as the TIP122, rated for 60v and 30A
since it is the same size, that meets the criteria of size for the OP

It costs $0.95 from Sparkfun, so is only slightly more expensive than the TIP122 from DigiKey ($0.61)

dave-in-nj:
a simple FET that is the same size as the TIP122, rated for 60v and 30A
since it is the same size, that meets the criteria of size for the OP

It costs $0.95 from Sparkfun, so is only slightly more expensive than the TIP122 from DigiKey ($0.61)

And if it's battery-powered, then a MOSFET is definitely the best option; because less of that power will be converted into heat. In other words, you will waste way less energy than with a TIP122; and also you can use a smaller heatsink than the requiered for the TIP122!

How many people need to tell you that a TIP122 is a BAD choice for anything low voltage.
Your compressor will only get 2/3 of the power. The transistor will dissipate the rest.
Leo…