doorbell
- Thread starter hwinther
- Start date
Rickharris
Senior Member
try wrapping a length of wire round one of the bell leads from the push button. The AC should induce a current you can measure - will need to rectify it woth a dipde though.
If you have a real bell there maybe enough RF rubbish generated by the bell to detect at close range - in fact it may upset the picaxe.
You could use a opto coupler as well - this will sepeate the AC from the picaxe and provide a neat digital signal.
If you have a real bell there maybe enough RF rubbish generated by the bell to detect at close range - in fact it may upset the picaxe.
You could use a opto coupler as well - this will sepeate the AC from the picaxe and provide a neat digital signal.
Assuming the 12V AC is from a standard transformer, you could use a bridge rectifier (4 diodes) , a smoothing capacitor, then a 5V regulator and another capacitor. Also a 220nF cap across the PICAXE +5-Gnd pins is a good move - especialy if you're going to conenct it to an RF Transmitter.
Not knowing anything else I don't know whether any noise suppression is needed.
I suggest a bridge rather than 4 diodes as you can get them in nice neat little packages eg <A href='http://www.vishay.com/docs/88571/dfm.pdf' Target=_Blank>External Web Link</a>
You may like to include a fuse to save embarrassment.
Not knowing anything else I don't know whether any noise suppression is needed.
I suggest a bridge rather than 4 diodes as you can get them in nice neat little packages eg <A href='http://www.vishay.com/docs/88571/dfm.pdf' Target=_Blank>External Web Link</a>
You may like to include a fuse to save embarrassment.
The doorbell circuit is usually something like this:
transformer terminal (o)-- button -- bell -- (o) other transformer terminal
If you want to isolate the PICAXE from the bell circuit, use an AC optocoupler or put pair of back-to-back LEDs (Led1 anode to Led2 cathode, Led2 anode to Led1 cathode) with a 2K resistor in series across the wires to the button. Use a photocell (or maybe another LED of the same type) as a light detector. The LEDs will normally be on. When the button is pressed they will turn off. The loss of light is the signal to activate the PICAXE.
John
transformer terminal (o)-- button -- bell -- (o) other transformer terminal
If you want to isolate the PICAXE from the bell circuit, use an AC optocoupler or put pair of back-to-back LEDs (Led1 anode to Led2 cathode, Led2 anode to Led1 cathode) with a 2K resistor in series across the wires to the button. Use a photocell (or maybe another LED of the same type) as a light detector. The LEDs will normally be on. When the button is pressed they will turn off. The loss of light is the signal to activate the PICAXE.
John
Far be it that I'd bypass a Picaxe approach, BUT you may even want to just replace the mains doorbell with a wireless one! The total cost may be less...
I'd much your need myself some time ago (back garden alert),& after pondering Picaxe solutions went with a 433.92 MHz based wireless door chime (ARLEC DC149)<A href='http://www.mitre10.co.nz/shop/lighting_and_electrical/electrical_outlets_and_fittings/wireless_door_chime_109195.cfm ' Target=_Blank>External Web Link</a> for just ~£7 ( NZ$20). Aside from it's great range (ahem- easily extended),the receiver has a snooze mode that cut battery drain to almost nothing (0.2mA). 2 AAs have now lasted a year, & show no signs of fading. The sender has a 3V Li coin cell,only activated when the doorbutton is pushed, implying a long life compared with previous 12V C-Zn mini battery powered senders.
Since the unit is so cheap & reliable, & has 4 code settings, I've even considered Picaxe hacking to utilise it's 433MHz tx/rx. Mmm- PV powered (ex. solar garden lamp) 08M IR "snail mail" post box alert? Stan in NZ
Edited by - manuka on 25/09/2006 02:37:50
I'd much your need myself some time ago (back garden alert),& after pondering Picaxe solutions went with a 433.92 MHz based wireless door chime (ARLEC DC149)<A href='http://www.mitre10.co.nz/shop/lighting_and_electrical/electrical_outlets_and_fittings/wireless_door_chime_109195.cfm ' Target=_Blank>External Web Link</a> for just ~£7 ( NZ$20). Aside from it's great range (ahem- easily extended),the receiver has a snooze mode that cut battery drain to almost nothing (0.2mA). 2 AAs have now lasted a year, & show no signs of fading. The sender has a 3V Li coin cell,only activated when the doorbutton is pushed, implying a long life compared with previous 12V C-Zn mini battery powered senders.
Since the unit is so cheap & reliable, & has 4 code settings, I've even considered Picaxe hacking to utilise it's 433MHz tx/rx. Mmm- PV powered (ex. solar garden lamp) 08M IR "snail mail" post box alert? Stan in NZ
Edited by - manuka on 25/09/2006 02:37:50
Yikes- price drop update: These are now just £5 (NZ$15) in NZ's "The Warehouse". Can someone over the ditch in Australia please confirm that these ARLECs are also being sold at much this price in Oz., as they'd make a great engine for a "Silicon Chip" Picaxe article. Ta- Stan
Edited by - manuka on 26/09/2006 10:22:48
Edited by - manuka on 26/09/2006 10:22:48
Even though the signal i got from the rectifier was good enough to be used as a switch i ended up making two separate circuits, one with a LED and the (picaxe one) with an LDR, and because the original doorbell casing is completely sealed off when closed, it works fine as a digital on/off switch. I will post an URL here later on when the project is more sucessful for anyone that would be interested.
Basically i connected another picaxe chip with a receiver to a computers serial port and "switched" the traffic over when it was transmitted to the right address. However, today the system "stopped working". And after fiddling alot with the setup, making an extra transmitter and removing anything unecessary, switching input pin etc, on the receiver breadboard, i finally found out it is receiving data, but at such a rate the legitimate stuff is being ignored.
Now finally on to my question; what kind of devices do you guys know of that would be using the 433MHz AM modulated band that could be sending continous data like this? Im thinking portable phones, alarm systems and maybe TV links, as i know alot of my neighbours use. And please if i am way off here let me know, i just want to get to the bottom of it.
Basically i connected another picaxe chip with a receiver to a computers serial port and "switched" the traffic over when it was transmitted to the right address. However, today the system "stopped working". And after fiddling alot with the setup, making an extra transmitter and removing anything unecessary, switching input pin etc, on the receiver breadboard, i finally found out it is receiving data, but at such a rate the legitimate stuff is being ignored.
Now finally on to my question; what kind of devices do you guys know of that would be using the 433MHz AM modulated band that could be sending continous data like this? Im thinking portable phones, alarm systems and maybe TV links, as i know alot of my neighbours use. And please if i am way off here let me know, i just want to get to the bottom of it.
Someone told me it could be e.g. a HAM radio or other equipment that operates on completely different frequencies but interferes now because its foggy outside.
I know i cant get an exact answer as there can be any number of things wrong here, but i did switch both the picaxe chip and the radio chip and made a new source code and breadboard layout just for receiving data..
But i dont know much about radio equipment, so is there anyone here who can tell me if the fog could be doing it?
I know i cant get an exact answer as there can be any number of things wrong here, but i did switch both the picaxe chip and the radio chip and made a new source code and breadboard layout just for receiving data..
But i dont know much about radio equipment, so is there anyone here who can tell me if the fog could be doing it?
hippy
Ex-Staff (retired)
433MHz is usually used in short range devices and with lowish power so it's more likely that the interference is coming from a local source rather than far away.
Atmospheric conditions can affect radio propogation and Stan/Manuka will tell you all about short range devices transmitting over long distances, but I suspect it's more local than that.
It could be almost anything from a jammed-on car keyfob or wireless doorbell, to a toy car transmitter, even another neighbour experimenting with PICAXE's or similar. Car key fobs, burglar alarms and similar usually use a different frequency to avoid being rendered inoperative by such jamming.
You could perhaps configure your PICAXE so you light a LED when data is received then go 'war driving' around your neighbourhood to see where reception cuts out. That may allow you to determine its source as being in the centre of the area approx. A directional aerial may allow you to find it through triangulation.
If you can prove that it is someone jamming the signal even if inadvertently ( take your setup miles away and see if it works as expected there ) you may be able to get the Radio Authority ( or whatever involved ) to find the culprit and sort it out or at least offer advice and some help.
Atmospheric conditions can affect radio propogation and Stan/Manuka will tell you all about short range devices transmitting over long distances, but I suspect it's more local than that.
It could be almost anything from a jammed-on car keyfob or wireless doorbell, to a toy car transmitter, even another neighbour experimenting with PICAXE's or similar. Car key fobs, burglar alarms and similar usually use a different frequency to avoid being rendered inoperative by such jamming.
You could perhaps configure your PICAXE so you light a LED when data is received then go 'war driving' around your neighbourhood to see where reception cuts out. That may allow you to determine its source as being in the centre of the area approx. A directional aerial may allow you to find it through triangulation.
If you can prove that it is someone jamming the signal even if inadvertently ( take your setup miles away and see if it works as expected there ) you may be able to get the Radio Authority ( or whatever involved ) to find the culprit and sort it out or at least offer advice and some help.
Interference is a function of distance as well as frequency. I used to receive taxi transmissions on my record player. Sometimes quite interesting.
Even a duff product from Ann Summers could cause interference.
Its a pity you weren't using FM modules with RSSI, then you could measure offending signals and in some circumstances optimise your antenna configuration to be a bit selective.
Say, I don't suppose your neighbour has been reading this thread and made himself a radio/PICAXE doorbell? With a 100kW transmitter?
Edited by - Dippy on 19/10/2006 15:35:06
Even a duff product from Ann Summers could cause interference.
Its a pity you weren't using FM modules with RSSI, then you could measure offending signals and in some circumstances optimise your antenna configuration to be a bit selective.
Say, I don't suppose your neighbour has been reading this thread and made himself a radio/PICAXE doorbell? With a 100kW transmitter?
Edited by - Dippy on 19/10/2006 15:35:06
inglewoodpete
Senior Member
I installed one of those radio doorbells a few years ago. (I put it in my junk parts bin a few months later). Apart from flaky operation (90% of button presses worked, 10% didn't), it would go off occasionally when we were using our(analogue) mobile 'phone. Sometimes it would go off when a car passed our house, possibly with a carphone in use. I installed a 'proper' doorbell with 'proper' wires connecting the switch to the sounder. Problem solved.
In your case, can you use the PICAXE to encode something at the sender (a couple of bytes), and then detect only that code at the receiver end? Or is the interference masking your reception?
In your case, can you use the PICAXE to encode something at the sender (a couple of bytes), and then detect only that code at the receiver end? Or is the interference masking your reception?
Ok... i tried using a 100K pull-down resistor between the RX data and ground lines, and it seems to do the job.
If i was supposed to have done that from the beginning then im sorry to have bothered everyone unecessarily.
However thanks for all the good input, and especially thanks to hippy for his picaxe wireless code
If i was supposed to have done that from the beginning then im sorry to have bothered everyone unecessarily.
However thanks for all the good input, and especially thanks to hippy for his picaxe wireless code