I have this 12V motor which i want to activate via arduino:
Max active time for motor is aprox 5 seconds. every 5 minutes (5 sconds is time motor need to move a gearbox to 2 full spins)
-Motor is powered with 12V 5A source
-arduino mega 5v from PC usb
i dont want to use relay and i want to use a transistor like a switch
1. what type of diode i need and why i need it?(so we can give an answer to me and others what it does and why is needed) 2. What type of resistor i need and why i need it? 3. what type of transistor i need and why ?
I try to search in aliexpress (there ill buy the parts) but they have different names and basically i dont know how to look for them
Which is best and cheapest solutions because i will have around 50 DC motors ( they will activate not more than 1 motor at a time)
Also there is imporant to know that i understand that motor made 2 full spins based on time (example i activate arduino pin for 4500ms). so i think voltage should be stable so i know exactly the time motor need to do those spins and thats need to be same every time.
1N4001 should be ok. But in your diagram you have the diode in the incorrect position. The diode should be across the motor terminals/pins, with the cathode connected on +12V terminal. The purpose of the diode is to protect the circuit from the negative voltage that will be generated by the motor when the current is switched off. The diode conducts that negative voltage so that reverse current does not flow into the rest of the circuit, which could damage some components (like the Arduino).
Connect 10K from the Arduino pin to ground and a 220R or 330R between the Arduino pin and the transistor base/gate. The 220/330R protects the Arduino pin from too much current. The 10K is only needed if the transistor is a MOSFET and it prevents the MOSFET from switching part way on when the Arduino pin is floating. If the MOSFET switches part way on, it can overheat, and the motor may twitch unexpectedly at startup.
I would recommend using a MOSFET such as IRLZ44 or similar. It should be n-channel and have a logic-level gate. MOSFETs are more efficient, run cooler and drop less voltage than BJT transistors, especially Darlington transistors.
A stable voltage will not guarantee that the motor will complete exactly 2 revolutions in 4500ms. Every motor is slightly different. To guarantee exactly 2 revolutions you will need a sensor to know when each revolution is completed. This sensor could be a microswitch to detect a bump in a wheel or an IR reflection sensor to detect a spot of white paint on a black wheel, for example.
ca u draw i diagram for the diode so i understeand better.
-can u tell us how we can search for transistors, diode and resistor what specification should we look on them
i think will be easier if we know what to look for insteand of just searching for IRLZ44.
example 3A 1000v or 5A 200v or specifications like this
Can you amend your diagram based on my description and I will tell you if you got it right.
You know from the specs of your motor what maximum voltage and current the transistor and diode need to work with. Take a look at the data sheets for the diode and transistor I suggested to see where these maximum values are listed.
Searching for suitable components with Google or any other search engine, based on the currents and voltages from your circuit, is unlikely to be successful. Some of the major component suppliers have pages where you can select components based on maximum values, but they are designed for experienced engineers to use, not beginners.
The resistors mentioned will carry voltages up to 5V and the currents will be very small, so standard 1/4W resistors should be fine, or even smaller ones if that helps. The resistance values do not need to be precise, so 10% precision components will be ok.
Make some experiments and decide for yourself if timing is accurate enough for your project. You may find that slight variations in supply voltage and temperature have an effect, and as the motor and gearbox age and wear, this also may have the effect of speeding up or slowing down that timing. Only you can decide if these variations are acceptable to you.
Correct. But as I mentioned, Darlingtons are much less efficient than MOSFETs and will probably slow your motor down a little. They will drop around 1.5V, leaving only 10.5V for the motor. They may also get hot and need a heatsink, although for only 5s running time, they should not get very hot.
Because it is not a true logic-level MOSFET, the IRF630 may not fully switch on with the 5V signal from the Arduino, and could also drop a significant voltage and get hot. A true logic-level MOSFET will have a gate threshold voltage of only 2~2.5V at maximum, which means that the 5V from the Arduino should get very close to 100% switched on, leading to a low voltage drop and very little heat.
Take a look at the data sheet for IRLZ44 and compare that to the IRF630.
thank you for your awsome answers, you are helping me and lot of peoples .
You know by yourself (by tests u have done) that voltage drop wil be around 1.5 or there is a way we can check/calculate voltage drop from datasheet / details of transistor before we buy
One drawback is an approximate doubling of the base–emitter voltage. Since there are two junctions between the base and emitter of the Darlington transistor, the equivalent base–emitter voltage is the sum of both base–emitter voltages:
For silicon-based technology, where each VBEi is about 0.65 V when the device is operating in the active or saturated region, the necessary base–emitter voltage of the pair is 1.3 V.
You can see that the gate threshold is maximum 2.0V, and with 5V on the gate, the resistance between the drain and source pins is only 0.025R. If your motor draws 0.28A, the voltage drop will be 0.28 X 0.025 = 0.007V. Even at stall current of 3A, the voltage drop is only 0.075V. Compare this to the 1.3V voltage drop of a typical Darlington transistor.
Here, the on-resistance is 0.045R with 5V on the gate, so not as low as IRLZ44, but still only 0.135V. that is still only 10% of the voltage drop of a Darlington.
