I have now got a vreg in operation. It is supplying 4.5V to three wireless doorbell receivers. Effectively replacing the 3 x 'AA' which once powered them.
The problem I have now is that using a multimeter, when connected to the wires which previously powered the 'speaker' + and -, I can read the 4.5v. The 4.5v lasts about eight seconds, the length of the receiver unit took to sound the doorbell.
However. If I tie the speaker grounds of these three doorbells together, and ring a doorbell - the multimeter shows a reading of 4.4v if I have my positive multimeter probe connected to the non-corresponding doorbell receivers and 4.5v if I have it connected to the corresponding receiver.
As far as the multimeter is concerned, in other words, with the speaker grounds tied the receiver units respond to any doorbell!
Isolated, they behave perfectly. That is, if I connect the negative multimeter probe to speaker - and the positive multimeter probe to speaker + I read 0v unless I press the CORRECT doorbell, at which point I get an 8 second pulse of 4.5v.
Similarly (this is where I thought I was going wrong) if I connect my multimeter negative probe to the vreg - and the positive multimeter probe to speaker +, I get a constant reading of 4.5v whether or not the doorbell is pressed.
So confused.
Have I possibly wired up the vreg wrong? It works very nicely for powering the receivers.
An update! If I connect the speaker + together (to my mind as if they were the speaker -) and connect THEM en masse (all three of them ) to multimeter plus probe, and individually connect the speaker - wire to the multimeter common probe, then things work as I would wish:
0v constant, 4.5v if correct doorbell button pressed lasting for 8s.
woody_unreal:
So. you have a Regulator outputing 4.5v one one unit, but when u hook it to more that one it drops ?
No, sorry, not at all must be my description.
JimG:
The switching transistor for the speaker is in an open collector configuration. That is, the switch is between -speaker and ground.
Jim - interesting. I take it that diagnosis matched my symptoms, so to speak? Where do I go from here? The only way I could effectively measure the voltage of each doorbell independently was to group the speaker positives - but can that work??
THANKS
Grumpy_Mike:
Sorry can't follow the words on what you did, do you have a schematic?
I've drawn a crude diagram of my setup. Does this help?
woody_unreal:
you may even try a actual picture it may be easyer to just find a walwart that is 4.5v
I will post an actual picture but it sounded/sounds to me like JimG was on to something!
As for finding a wall wart that is 4.5v, that's what I thought. Then I found that a wall wart for 4.5v can output +/- roughly 3v in either direction! Hence the vreg. I don't think the problem lies in my vreg, though.
woody_unreal:
Random thought , whats the output of the Walwart ?
It's rated at 9v and 1A.
I humbly suspect that the vreg is not the issue. I think I can get a usable reading from the configuration I described earlier but two things worry me 1) what happens if I need to tie new grounds together 2) I have now departed from a place where I understood why things worked.
Hm Well if your drawing is accurate... the DC Grounds should always be tied togeather unless being Switch or ajusted. You had said something about the Negative being use as switch. Also Do you think the VReg can handle the Load ?
With nothing powered on, use your multimeter to check continuity on each speaker unit:
From Vcc to +speaker
From -speaker to GND
I'm guessing that Vcc to +speaker will be a short (no resistance), and -speaker to GND will be open. It seems likely that the speaker units use a simple NPN transistor (or N-channel FET) between -speaker and GND. Putting a signal on the base of the NPN, presumably triggered by pressing a doorbell button, causes the NPN to conduct, which connects -speaker to GND. This completes the circuit and causes the speaker to speak.
When you connected all of the -speakers together, then triggering any one of the NPN transistors would have connected all of the -speakers to GND. This is what you experienced, right?
To be honest, though, I really have no idea what you are trying to accomplish?
JimG:
With nothing powered on, use your multimeter to check continuity on each speaker unit
Hi Jim
I think you are right. With nothing powered on there was continuity between vdd and speaker +. There was not continuity between - speaker and GND.
As for what I'm trying to accomplish - I am trying to use wireless doorbells as wireless buttons (i.e. digital inputs).
I'm now wondering how I should wire these up to the Arduino. I had intended to connect the speaker + contacts to digital input pins and tie all of the speaker- to ground - but this is obviously is a no go.
With nothing powered on there was continuity between vdd and speaker +.
I would not take too literally the + an - markings on the speakers. It all depends on the circuit of the amplifier output stage. When you measured the continuity did you do it in both directions? That is swap the leads around to make sure you were not going through a semiconductor PN junction.
However it is possible that the speaker is connected to the +ve rail of the supply and it is pulled down by the output stage. This will result in a square wave type signal.
For what I is worth I don't think your problems are with the 4.5V regulator either, mind you I think it will work just as well off 5V as 4.5V.
I had intended to connect the speaker + contacts to digital input pins and tie all of the speaker- to ground
So why not connect the speaker - to the arduino input pins and all the grounds together, would that not do it?
Grumpy_Mike:
I would not take too literally the + and - markings on the speakers. It all depends on the circuit of the amplifier output stage. When you measured the continuity did you do it in both directions? That is swap the leads around to make sure you were not going through a semiconductor PN junction.
However it is possible that the speaker is connected to the +ve rail of the supply and it is pulled down by the output stage. This will result in a square wave type signal.
For what I is worth I don't think your problems are with the 4.5V regulator either, mind you I think it will work just as well off 5V as 4.5V.
So why not connect the speaker - to the arduino input pins and all the grounds together, would that not do it?
Mike - I REALLY value your help. Just wanted to say so.
I didn’t swap the probes when measuring continuity. Will do so when I get home.
Can I clarify? Did you mean to
A) connect the “speaker–“ to an input pin and tie the vreg ground to the arduino ground?
B) connect the “speaker–“ to an input pin and tie the speaker + to the arduino ground.
I agree the speakers will work equally well from 5v (I tried it and it works). But I am worried about overloading the ethermega (my Arduino variant) because I would be asking it to provide power for six LEDs, five wireless doorbell receivers, one servo and one ethernet ‘shield’.
It is option A that I meant.
The thinking is that if the speaker + is connected to Vcc, grounding that will short your supply, so don't do it. In normal operation the speaker - will be being pulled to ground by the circuit inside the door bell so you can use that to detect the speaker is producing some sound. You might have to add a pull down resistor from the speaker - and arduino input to ground, depending on the circuit inside the bell.
As long as the ground on the bells and the ground on the arduino are common you should be OK. So you should not be connecting the speaker + anywhere.
Confirm assumed internal configuration of speaker boxes first:
Connect 5VDC wall wart outputs to the power terminals (VCC and GND) of the speaker box.
Measure voltage from -speaker to GND
a) should be nearly Vcc when button is not pressed
b) should be nearly GND when button is pressed (will probably be 0.5V or so).
If you confirm those measurements, then just connect -speaker to an Arduino digital input pin. Signal will go low when button is pressed, but will otherwise be read as high.
Jim
PS - don't disconnect the speakers unless you put load resistors (10K maybe) in their places. Otherwise you will short Vcc directly to GND when a button is pressed.
EDIT -- Oops, did not see before I posted that Mike had already responded with an identical suggestion.
JimG:
PS - don't disconnect the speakers unless you put load resistors (10K maybe) in their places. Otherwise you will short Vcc directly to GND when a button is pressed.
Do you mean the actual physical speaker unit here? Because if so, I've done exactly that. I've clipped off the speaker. So you say I need to have a 10K resistor between the two dangling wires?
Things work as they are currently configured - but I guess I'm reducing the longevity of the speaker unit at the moment? Or?
) to multimeter plus probe, and individually connect the speaker - wire to the multimeter common probe, then things work as I would wish:
