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Simple RF M4 Receiver - Won't work from further than 4"
Moderators: adafruit_support_bill, adafruit

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Re: Simple RF M4 Receiver - Won't work from further than 4"

by adafruit_support_bill on Wed Mar 03, 2021 3:02 pm

What is the output voltage on the pin if you remove the LED from the circuit?

50' should be no problem for the RFM69HCW Packet Radios.

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Re: Simple RF M4 Receiver - Won't work from further than 4"

by pete_projects on Wed Mar 03, 2021 5:45 pm

With removing the LED from the circuit and measuring at the output, it's consistently at 4.3V up to around 30'. I'll note that I get the same behavior with all the LED's flickering and showing a lower voltage (all the outputs), so I don't think it's an intermittent connection. I'm using 220 ohm resistors with the LED's. Any thoughts on what I'm missing there?

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Re: Simple RF M4 Receiver - Won't work from further than 4"

by adafruit_support_bill on Wed Mar 03, 2021 8:21 pm

The outputs of the M4 receiver are 'logic level'. The chip manufacturer does not have a spec for how much current they can source. With a weaker signal, the output pins source less current so the output voltage will sag when loaded. To switch more current to the load, you could connect a small transistor to the output signal.
Attachments
pn2222.png
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Re: Simple RF M4 Receiver - Won't work from further than 4"

by DPKJr on Wed Mar 03, 2021 9:50 pm

Here is what I am trying now.

Receiver
RXM-433-KH3
https://linxtechnologies.com/wp/product ... r-modules/

Transmitter
OTX-433-HH-KF#-HT
https://linxtechnologies.com/wp/product ... ansmitter/

Working through soldering headers and setting addressing on devices.

Doesn't seem like it would be such a PITA to get a button to work. What do garage door openers and car remotes all over the world use?

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Re: Simple RF M4 Receiver - Won't work from further than 4"

by pete_projects on Mon Apr 05, 2021 11:32 pm

adafruit_support_bill wrote:The outputs of the M4 receiver are 'logic level'. The chip manufacturer does not have a spec for how much current they can source. With a weaker signal, the output pins source less current so the output voltage will sag when loaded. To switch more current to the load, you could connect a small transistor to the output signal.


I tried this, and I can get the light to flicker more brightly, but I'm still getting a flickering with a red LED more than maybe 6" away. I tried with a second M4 Receiver to confirm it didn't seem to be unique to the device, and the same happened with the 2nd receiver. I'm using the 10mm diffused LEDs from here. (https://www.adafruit.com/product/4204). Tried a couple different resistances, but same issue with flickering. Am I accurate to assume this is just a limitation with the receiver and I should move on to trying this with two Feather 32u4 I got for a better version of my project to remotely control LED's with a remote?

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Re: Simple RF M4 Receiver - Won't work from further than 4"

by adafruit_support_bill on Tue Apr 06, 2021 5:50 am

When you say flickering, do you mean a constant flicker or a periodic - every few seconds flicker? A periodic flicker is normal for these devies as the transmitter periodically re-transmits the code.

Have you extended the coiled antenna? For best reception it should be extended straight and in a vertical position.

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Re: Simple RF M4 Receiver - Won't work from further than 4"

by pete_projects on Wed Apr 07, 2021 11:06 am

adafruit_support_bill wrote:When you say flickering, do you mean a constant flicker or a periodic - every few seconds flicker? A periodic flicker is normal for these devies as the transmitter periodically re-transmits the code.

Have you extended the coiled antenna? For best reception it should be extended straight and in a vertical position.


The red LED is flickering constantly if the remote is more than a few inches away. I'm not seeing a way to add a video, but in a quick video is was about 4 times a second flickering on/off. I've got the 2N2222 in the circuit for the red LED, but that didn't solve the flicker. Rload = 100 ohm, Rbase = 2 k ohm. The voltage I was measuring at the output was 4.5V.

Yup, the antenna is extended to a vertical position.

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