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Topic: External Power Supply on RF 315/433 MHz Transmitter-receiver Module (Read 5295 times) previous topic - next topic

OldSteve

The data sheets for those cheap 433 Mhz transmitter / receivers are a bit confusing.
The 3 - 12 V spec applies to the Transmitter only.
The receiver needs 5V regulated and the super regen receivers (the ones without a crystal) are the most critical , voltage wise.

What's confusing? The datasheet does clearly say 3-12V for transmitter and 5V for receiver. (4.9V-5.1V in my datasheet)

I only mentioned powering the transmitter with 12V. I used 5V on my receivers, which suited the PIC chips that I used to control this system. (And the usual Arduino setup, of course, but I hadn't started using Arduinos when I built the alarm systems.)

But you raise a good point that I overlooked - DrAzzy used 3.3V on both ends. :(
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alex52

One last question, I'm using the cheap moisture sensor YL-69. It will be plugged on the arduino board of the receiver, it will send data every hour to a database. However, I know that this sensor get damage easily, so I want to power it only when I read the data (when it will send the data every hour). Do you have an easy way to do that ? I need to use a digital pin right ?


DrAzzy

What's confusing? The datasheet does clearly say 3-12V for transmitter and 5V for receiver. (4.9V-5.1V in my datasheet)

I only mentioned powering the transmitter with 12V. I used 5V on my receivers, which suited the PIC chips that I used to control this system. (And the usual Arduino setup, of course, but I hadn't started using Arduinos when I built the alarm systems.)

But you raise a good point that I overlooked - DrAzzy used 3.3V on both ends. :(
Not even, in some tests ;-)
I got >800' (LoS) with 2.1v on the transmitter! (one of the cheap green transmitters, too - with a good receiver, ofc)
ATtiny core for 841+1634+828 and x313/x4/x5/x61/x7/x8 series Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts (some assembled), mosfets and awesome prototyping board in my store http://tindie.com/stores/DrAzzy

OldSteve

Not even, in some tests ;-)
I got >800' (LoS) with 2.1v on the transmitter! (one of the cheap green transmitters, too - with a good receiver, ofc)
Wow, that's not bad. I've never gone lower than 5V with a transmitter, and as mentioned, usually 12V for extra oomph.

Actually, apart from for very simple stuff like remote control, I usually use the APC220 modules that I mentioned. A lot more expensive, but they're more reliable, support serial baud rates up to 115200, RF TX rates to 19200, (on-board buffer), and most importantly, the frequency is firmware-configurable, allowing multi-channel use. Pretty handy.
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OldSteve

One last question, I'm using the cheap moisture sensor YL-69. It will be plugged on the arduino board of the receiver, it will send data every hour to a database. However, I know that this sensor get damage easily, so I want to power it only when I read the data (when it will send the data every hour). Do you have an easy way to do that ? I need to use a digital pin right ?
I doubt if simply leaving the moisture sensor powered will damage it.

Still, if you want to intermittantly power it from the Arduino, it shouldn't be too hard. How much current does it use? If 20mA to 30mA or less, you could connect an Arduino analog pin directly to it's Vcc, then just use digitalWrite(pin,1) to turn on the sensor. (digitalWrite(pin,0) to turn it off, of course.

Do you have a link to the sensor module's datasheet?
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alex52

I just tried to find one on the internet but no luck so far. The name of this sensor is the YL-69.

But the analog pin can deliver 5V too?

Edit: I found this doc : http://eie.uonbi.ac.ke/sites/default/files/cae/engineering/eie/MICROCONTROLLER-BASED%20IRRIGATION%20SYSTEM.pdf

It says 35 mA. Should I use a transistor to give more current ?

OldSteve

I just tried to find one on the internet but no luck so far. The name of this sensor is the YL-69.

But the analog pin deliver 5V?
Why would you use an analogue output? A digital pin supplies 5V. (Absolute maximum 40mA, so up to about 30mA would be fine. (I'm assuming that the sensor needs a 5V supply voltage.)
You just need to ascertain how much current the sensor uses. You could use a 1Ω to 10Ω resistor in series between the +5V and the sensor's Vcc pin, then measure the voltage developed across it to determine the sensor's current consumption. I = V / R

Edit: Where did you buy the YL-69? They might have the specs.
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OldSteve

I just got a diagram for the YL-69, (attached). I expected an analogue output, but it looks like a digital output, set around an adjustable threshold.
If your's is the same, (using an LM393 comparator, and with two LEDs), you will be fine to use an Arduino digital pin to power the module via it's Vcc connection.

It has two LEDs, but they have 1K series resistors, so will only use roughly 3mA each. The rest of the circuit uses negligible current.
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alex52

Oups, yes Steve I meant the digital pin, I didn't know it supplies 5V. I've edited my previous message, I found a source. I bought it in the chinese market directly at a small shop ^^

I'm not sure its the same, mine has a comparator with VCC, GND, Analog and Digital output (Same than the one on the doc I've posted)

OldSteve

Oups, yes Steve I meant the digital pin, I didn't know it supplies 5V. I've edited my previous message, I found a source. I bought it in the chinese market directly at a small shop ^^

And yes my sensor is the same with the comparator
Good, no problem then. Use one digital pin as an output to power it, and another configured as an input to receive the sensor's digital output.

You edited your reply and now say your's is different. This is getting confusing.

I see, you also went back and edited an earlier post to include a link to the 56-page pdf document of someone else's project. I'm not interested in searching through that to find information.

Just measure the current consumption of your module. If it uses 30mA or less, use a digital pin as suggested to power it, then an analogue or digital pin to read it's output, depending on which you want.

I can't see how it could be damaged as you claim, by keeping it permanently powered.
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alex52

Yes, sorry... I bought exactly the same than this one in the tutorial : http://www.instructables.com/id/Soil-Moisture-Sensor/?ALLSTEPS

I'm new to this, I'm a bit confused too, I've started recently.

OldSteve

Yes, sorry... I bought exactly the same than this one in the tutorial : http://www.instructables.com/id/Soil-Moisture-Sensor/?ALLSTEPS

I'm new to this, I'm a bit confused too, I've started recently.
You keep sending me to read other people's projects. I can answer simple questions, but don't have the time to do an in-depth study. Just do as I suggested in my last reply. That's the best solution.
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alex52

It could be damaged by corrosion, that's what I've seen a lot in other projects, a lot of people advice to do that from what I've seen.

Ok, I see, thanks a lot for your help! I'll try what you said :)

Sorry for the bothering OldSteve. I'm trying my best on this!

OldSteve

It could be damaged by corrosion, that's what I've seen a lot in other projects, a lot of people advice to do that from what I've seen.
Right, I guess that's possible, from electrolysis.

Quote
I'll try what you said :)
That's the best thing. Only takes 1 minute, and then you know exactly how much current it uses.
More than likely it will be under 30mA, but better to be sure than sorry. :)

(I don't have a lot of time right now because I'm working on my project, preparing to make some PCBs. I need to get two PCBs made, then drilled and assembled today ready to use tomorrow. That's why I couldn't read the pdf document and go through the instructable you linked.)
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Whandall

If you keep the sensor powered all the time, it will be destroyed in under a month.
I learned that from experience.  :smiley-confuse:
Ah, this is obviously some strange usage of the word 'safe' that I wasn't previously aware of. (D.Adams)

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