Simple RF M4 Receiver connection question

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Shayne82609
 
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Simple RF M4 Receiver connection question

Post by Shayne82609 »

I have a Simple RF M4 Receiver ID:1096 that I want to control 2 small motors via 4 relays.

Here's the circuit I have in mind. Is it correct? I have left off the motor wires for clarity. Do I need to add any resistors or capacitors to this system with the relay coils?
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adafruit_support_bill
 
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Re: Simple RF M4 Receiver connection question

Post by adafruit_support_bill »

What is the rating for the coils on those relays? If it is more than 20 mA or so, you will probably need a transistor to drive the coil. In any case, you will want to add a diode to each relay circuit to protect against the reverse voltage spike generated when the coil is de-energized. A typical circuit would be similar to the one here: http://makezine.com/2009/02/02/connecti ... o-arduino/

Shayne82609
 
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Re: Simple RF M4 Receiver connection question

Post by Shayne82609 »

Nominal coil current is 89.3mA. Will probably need a transistor per relay in the system then. With a transistor, will I still need the diodes?

The other concern I have is the voltage requirement. The datasheet on the PT2272 says 4-15 Volts. I assume since this receiver is advertised as 5v there is something else limiting the voltage. I would like to power the motors and the receiver with a 4xAA battery pack (4x1.5v = 6v nom.). Would this cause any problems, or do I need to drop the voltage first?

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adafruit_support_bill
 
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Re: Simple RF M4 Receiver connection question

Post by adafruit_support_bill »

A small transistor such as a PN2222 should do the job: http://www.adafruit.com/products/756
You still need the diode to protect the transistor: http://www.adafruit.com/products/755
The datasheet on the PT2272 says 4-15 Volts. I assume since this receiver is advertised as 5v there is something else limiting the voltage.
The chip itself is rated for 4-15v. The complete receiver module is rated for 5-10v. A 4xAA battery pack will work fine.

Shayne82609
 
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Re: Simple RF M4 Receiver connection question

Post by Shayne82609 »

Something like this work? Check my polarities, I may have screwed them up.

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adafruit_support_bill
 
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Re: Simple RF M4 Receiver connection question

Post by adafruit_support_bill »

Your diodes should be in parallel with the coils as in the diagram here: http://makezine.com/2009/02/02/connecti ... o-arduino/

Shayne82609
 
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Re: Simple RF M4 Receiver connection question

Post by Shayne82609 »

ah! I thought something didn't look right. I'm still learning this sort of thing. You'll have to forgive the noobie mistakes :)

Like this?

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adafruit_support_bill
 
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Re: Simple RF M4 Receiver connection question

Post by adafruit_support_bill »

Looks like you are also missing the base resistors. For a 2n2222, 1Kohm should work.

Shayne82609
 
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Re: Simple RF M4 Receiver connection question

Post by Shayne82609 »

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adafruit_support_bill
 
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Re: Simple RF M4 Receiver connection question

Post by adafruit_support_bill »

That looks better! :)

Shayne82609
 
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Re: Simple RF M4 Receiver connection question

Post by Shayne82609 »

very cool. I'll run with it then. Thank you for the help on this

icarus691
 
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Re: Simple RF M4 Receiver connection question

Post by icarus691 »

May I ask why you grounded VT? Documentation shows this as an output driving a LED to show receiver activity.

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adafruit_support_bill
 
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Re: Simple RF M4 Receiver connection question

Post by adafruit_support_bill »

May I ask why you grounded VT? Documentation shows this as an output driving a LED to show receiver activity.
Good catch. That output should be left open - or you can connect an indicator led if desired.

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