[SOLVED] Wireless signal from a tempertaure switch

[anandpv2009]

You can use those ICs with the same modules.

 

[Englewood]

Cheers , so if I get the ICs and set it up like the drawing will the LED stay on over temp and go off under temp?

 

[anandpv2009]

Yes, if your temp sensor's out is logic high/low after threshold and logic low/high below threshold.
any change in Dx will reflect on Dx OUT of receiver

 

[Englewood]

I presume so as it just a switch off or on (High or Low)

 

[anandpv2009]

Yes, high and low states only.

 

[Englewood]

I seem to get a lot of interference - how can I reduce this?

I have used a cap from data out to gnd on the reciever

 

[Englewood]

Sorted with capacitors just a small bit now.

 

[anandpv2009]

I seem to get a lot of interference - how can I reduce this?

I have used a cap from data out to gnd on the reciever

Output of those cheap RF module will never be stable or error free unless you use a good coding technique. Since you don't have controllers in your circuit the only possible solution is HT12E/12D pairs.

 

[Englewood]

**broken link removed****broken link removed**

Check these 2 circuits.
Instead of switch connect your temp sensor on/off pin. (high/low states)
Transimitter Receiver
D0 - D0 OUT
D1- D2 OUT
D2 - D3 OUT
D3 - D4 OUT

I have received my 2 IC's now.

I need the temp switch on the transmission IC, so when the temp reaches 60c the switch closes and a signal is sent to the receiver to turn a led on.

Where would put the temp switch?

From D0 to ground? so when the switch close it sends a signal?

 

[anandpv2009]

1. Connect you temp switch on an of the pins (D0 or D1 or D2 or D3 or D4) and the corresponding out pins at the receiver will change with switch state.

Example.
If you connect your temp switch on D0 (HT12E) then D0 OUT of HT12D will change its state with change on D0 pin.

 

[FvM]

Connect you temp switch on an of the pins (D0 or D1 or D2 or D3 or D4) and the corresponding out pins at the receiver will change with switch state.

Only if the transmitter is permanently enabled by shorting /TE to ground, causing respective current consumption and blocking concurrent RF devices. According to regulations, more than 10 percent duty cycle isn't permitted.

Instead you'll want to either activate the transmitter periodically, or periodically only if the temperature limit switch has tripped.

 

[Englewood]

Okay,

I've had a test, I've wired up my circuit but if D0 on the transmitter is open its sends a constant signal to D0 on the receiver.

If D0 is closed it doesn't send a signal.

I need this to do the opposite, if D0 is open it doesn't send a signal but if D0 is closed it sends a signal.

 

[FvM]

A transistor can invert the switch polarity. Using a MOSFET, the quiescent current can be very low, e.g. a few µA.

I believe, the encoder and transmitter supply must be switched too to achieve an acceptable battery lifetime.

 

[Englewood]

Or I can just used a normally closed temp switch and when the switch opens it activates the receiver

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Can I use a different value resistor than a 750K

 

[anandpv2009]

Or I can just used a normally closed temp switch and when the switch opens it activates the receiver

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Can I use a different value resistor than a 750K

You can use 1M resistor. Just use any values near 1M (RC oscillator)

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Or I can just used a normally closed temp switch and when the switch opens it activates the receiver

As FVM said, better use your temp switch to ON supply transmitter and HT12E supply if it is a battery operated device.

 

[Englewood]

Yes just realized this, I'm using a CR2032 for the transmitter and I cant have it constantly on so I will put the Temp switch as a switch to turn on the transmitter.

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Strange:.

When there is no power to the transmitter the receiver stays on!.

When I put power the transmitter circuit the receiver stays on, unless I connect D0 to ground then it switches off.

If I have D0 constantly connected to ground the receiver stays off.

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This is what happens, the LEDS stay on but when I press the switch they go off? how can I reverse this :-S

https://www.youtube.com/watch?v=pMyWpTtm3VQ&feature=youtu.be

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Doh - all had to do was take the LED OUTPUT to +5 volts instead of ground.

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How much current will be drawn from the batter when the /TE is constantly on or will it only draw current when data is sent?

 

[d123]

The datasheet should hopefully say in the electrical specifications Ioh and Iol, something like those terms, Current Out High and Current Out Low, I guess there will be separate fields in the datasheet both for current used for the device just to function and to define current draw on pins that do something, also there is quiescent current which might be of interest to you. Sometimes have to (in my case, struggle) to add up all the current drawn by the device at any one time of operation in order to calculate the total that is the point of interest to you.

 

[Englewood]

Hello D123, I hope your well.

Yes, was very late last night and my mind wasn't thinking clearly.

As far as I'm aware my circuit is working the way I want it too work apart from the circuit is constantly drawing current from the battery from the transmission enabled.

I can use a switch to turn the device on or off.

I wanted to try and incorporate the power to the battery through the temp switch so it allows current to flow when closed and also enables the sending of data.

 

[d123]

Hi dude, hope you're well too.

FvM said a MOSFET could invert the switch polarity.

I don't understand your circuit much, but if transmit is always on and wasting valuable battery current, if that's what's happening, could you maybe use the temp switch to trigger the transmission enable when it's needed? Possibly could do so but may need additional switch/"watchdog/wake up and do something" type device to do so, random and not well-thought out idea is something like a tri-state switch (meaning switch with enable, and that may be the reference to the MOSFET in post #33) between power, temp switch and transmit enable - sorry if the suggestion is useless as I am guessing how to fit the pieces together.

 

[d123]

Hi again. If I understood you well, maybe the attached image is what you want to do with the pushbutton binary morse code transmitting device - that's what it looks like it does in that simplified schematic!

Anyway, I think this is what you meant, I assume it works okay for your needs. Transistor as a switch. (Are you still using a wireless relay?, I'm unsure, if so you'd need to modify the schematic) If the temp switch isn't high voltage then a 2N3904 or a BC547 should be enough if you use a BJT, you'd need to explore MOSFET options yourself.