How to Drive 5V DC Motor Using PT2272 RF M4 Receiver 315MHz Output Pins?

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#1 21671346 19 Apr 2014 21:28

Ramien Ebadypour Ramien Ebadypour

Anonymous

Post #1
21671346 19 Apr 2014 21:28

Hi there, im new here and new to ee design.

I just purchased a simple RF M4 Receiver 315 MHz momentary device:
https://www.adafruit.com/products/1096 and remote.

I have a small 5V DC motor connected to one of the 4 data pins. When i activate the pin (high) i get the correct 5V output, but the output isnt turning on the motor. I assume I'm doing this wrong. Im sure this comes down to some basic ee principals of design. I've attached a picture for reference. The pic doesnt show it but i have 5v on the rail.

Any help would be appreciated. Thanks!
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#2 21671347 22 Apr 2014 10:04

Joshua Bishop Joshua Bishop

Anonymous

Post #2
21671347 22 Apr 2014 10:04

Hey Ramien, I think this may be a simpler solution than what has been discussed so far. I imagine the problem is that your receiver can probably only source or sink something along the lines of 20mA, whereas your motor will draw 10 to 100 times that much current. Your receiver just can't give it enough power.

If you have a solid 5VDC supply that you're running your receiver on, you can just use an N-channel MOSFET as a switch. Connect the motor to 5V and the drain of the MOSFET, ground the source, and hook the gate of the FET to the output of your receiver. When the output of the receiver goes high, it should "close" the switch and allow the current to flow from 5V, through the motor, through the FET to ground.

Careful, though, as the motors can make your 5V source kind of dirty and may put out interfering EMI. Good luck!
#3 21671348 22 Apr 2014 18:08

Ramien Ebadypour Ramien Ebadypour

Anonymous

Post #3
21671348 22 Apr 2014 18:08

Thank you Joshua. Is there a specific mosfet that i need for my application? I attached a list from NTE and there are tons to choose from. Which one is best? Thanks I appreciate your help.
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#4 21671349 22 Apr 2014 18:28

Ramien Ebadypour Ramien Ebadypour

Anonymous

Post #4
21671349 22 Apr 2014 18:28

Is this circuit design correct? Do i need a resistor inline?
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#5 21671350 22 Apr 2014 18:31

Ramien Ebadypour Ramien Ebadypour

Anonymous

Post #5
21671350 22 Apr 2014 18:31

Actually i think i made a mistake, motor should tie to 5v not ground, correct?
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#6 21671351 23 Apr 2014 09:37

Joshua Bishop Joshua Bishop

Anonymous

Post #6
21671351 23 Apr 2014 09:37

Ramien, the updated drawing that shows the motor being connected to 5V is correct, no resistor necessary. It should work as it is, though I would recommend looking into flyback diodes so you don't fry your receiver. I don't think the problem is the power supply, or at least that wouldn't be my first thought.

I don't know which MOSFET would be best for this application, there are a lot to choose from. The switching speed won't be important for this application as it won't be switching quickly. Just make sure that the Gate voltage is less than 5V and that the Drain to Source current can handle at least a couple Amps, probably 4 or 5 amps to be safe. So you're probably going to be looking into power FETs. See what you can find and post it here and I'll look at it and hopefully some other people with experience.
#7 21671352 24 Apr 2014 14:14

Ramien Ebadypour Ramien Ebadypour

Anonymous

Post #7
21671352 24 Apr 2014 14:14

So here is my current schematic diagram 1 (1 power source). Everything is working, except the transceiver isn't communicating well with receiver - receiver problem. The Mosfet design was the right path. I also added a rectifier to prevent damage to motor.

Now, I want to run the receiver and moto off separate power sources but whenever I connect the motor to another source via diagram 2 attached, it doesn't work. Ideas?
#8 21671353 24 Apr 2014 14:36

Joshua Bishop Joshua Bishop

Anonymous

Post #8
21671353 24 Apr 2014 14:36

Hey Ramien, that's getting closer. I realize that the schematic doesn't necessarily reflect the physical layout of the circuit, but I just want to emphasize that the Drain and the Source for the FET, where the current goes, needs to be connected to the battery, not the receiver.

Using the separate power supply, the problem is a lack of shared ground. Remember that voltage is all relative. Since you have two separate and unconnected power supplies, they're "floating" at different potentials. Easiest way to fix that is to attach ground on both supplies together, giving them the same reference as a basis. The problem with that is that the noise introduced to one power supply is transferred to the other.

Speaking of which, it's been awhile for me but I'm pretty sure that should be some sort of zener diode for the protection.
#9 21671354 24 Apr 2014 15:27

Ramien Ebadypour Ramien Ebadypour

Anonymous

Post #9
21671354 24 Apr 2014 15:27

Yes good catch, I will update and show you the true diagram layout. Yes Zenner diode was used as I recall. I need to confirm the NTE# as the diagram I provided is not correct.
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Topic summary

A user seeks to drive a 5V DC motor using a PT2272-based RF M4 Receiver operating at 315 MHz, connected to one of the receiver's data output pins. The receiver outputs 5V logic signals but cannot directly power the motor due to limited current sourcing capability (~20mA), while the motor requires significantly higher current. The recommended solution involves using an N-channel MOSFET as a low-side switch: the motor connects to 5V, the MOSFET drain to the motor, source to ground, and the gate driven by the receiver output. This configuration allows the MOSFET to switch the motor current safely. No inline resistor is necessary on the gate, but a flyback diode (rectifier) across the motor terminals is advised to protect the circuit from voltage spikes caused by motor inductance. When using separate power supplies for the receiver and motor, a common ground reference is essential to ensure proper operation and avoid floating voltage levels. Additionally, a Zener diode may be used for further protection. The discussion includes schematic verification and component selection advice, emphasizing MOSFETs capable of handling at least 4-5A with gate voltages compatible with 5V logic.
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How to Drive 5V DC Motor Using PT2272 RF M4 Receiver 315MHz Output Pins?

How to Drive 5V DC Motor Using PT2272 RF M4 Receiver 315MHz Output Pins?

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