... I suppose part of my question is why I would want to use a regulator over a buck or vice versa. Hence although it might not make a difference in practical terms, having something that's as efficient as can be would make me feel warm and tingly inside.
I said "SoC module" because I'm still not sure what I'll be using - I'll probably settle on a Wemos D32, but it might be a D1 Mini Pro instead.
I actually had a look at the schematics and I think they all use a ME6211 which operates on a voltage range of 2-6v which sounds too narrow for a rectified 8vac?
The resistance across the AC chime terminals (I tested both also while button was pressed which I assumed shouldn't matter but did it anyway) is around 4 ohm
The voltage at across one of the chimes when the button is pressed is around 6.4V
...but according to the above it draws around 1.6A (6.4v/4ohm), which sounds pretty high.
What you tested is the DC resistance. AC resistance, or reactance is the quantity in play. That 100Ω on the label is, likely, the AC resistance at 50 or 60 Hz [depending on your locale].
Not at all. 8VAC will easily accommodate that voltage range, as long as the 8VAC source can supply the required current. But, of course, a regulator will be required.
Thank you both for the responses. Interestingly I can connect a 9V battery to it but I suppose something else is going on there.
so I have no explanation for the 200mA disparity between the 1A rating and the 800mA math result.
Probably wise if you just want to get something going. But better to choose a higher voltage wallwart ( 8-15v)and feed it into the Vin of the arduino - it's internal high quality linear regulator will take care of the rest....
For a smart doorbell project, I'm considering using a uninterrupted 8VAC supply to provide power to a SoC module and some relays.
A quick google came up with this:Which seems to do the trick, but uses an L7805. Is this the best way to achieve what I need? I ask because I read that it's pretty inefficient.
As an alternative I also spotted this:
But partly as a learning exercise, I'm wondering if I can do better by building my own, based on this:https://electronics.stackexchange.com/questions/97571/how-to-convert-6v-ac-to-5v-dc
At 8VAC, the resulting DC will be 8 x 1.414 ~ 11.31 - 1.4 ~10v. I was hoping to just use a buck after this point like this:
But do I still need the various capacitors? If so, how can I work out which ones?
Also can I use 1N4148 for the rectifier bridge?
I said "SoC module" because I'm still not sure what I'll be using - I'll probably settle on a Wemos D32, but it might be a D1 Mini Pro instead. I actually had a look at the schematics and I think they all use a ME6211 which operates on a voltage range of 2-6v which sounds too narrow for a rectified 8vac
Also looking around I can expect these to draw around 800mA peak since they'll be using the WiFi a bit.
The transformer idles at 9VIt's a DAT03A which is rated at 2AWhen the button is pressed the voltage drops to 8.7V.
And for the chimes:The label of the chime says AC 8V ~ 1A
The voltage at across one of the chimes when the button is pressed is around 6.4V[/li][/list]
I can't seem to measure the current with my multimeter (I later realised it only works with DC), but according to the above it draws around 1.6A (6.4v/4ohm), which sounds pretty high.
So unless my schoolboy testing is in error, it sounds like the transformer shouldn't be able to provide enough current for the two chimes let alone the WeMOS/ relays. Am I missing anything?
Interestingly I can connect a 9V battery to it but I suppose something else is going on there.
I'm still a little confused about this.
The Ardiuno Uno seems to use this lp2985-33dbvr which takes in 16V which sounds quite handy.
However the ESP32 board I'm looking at has a ME6211 (https://wiki.wemos.cc/_media/products:d32:sch_d32_v1.0.0.pdf) which seems to take in 6v max, which I presume means the 8-15v is out?
Why would I go for a higher voltage anyway? For more options later? If it is handy to have then I can externally step down the input to 3.3v for the ESP32 (using what? A lp2985-33dbvr?).
I also need 5v to feed the relays, though, so if I stuck to the 5v looking at the schematic or board photo (https://wiki.wemos.cc/products:d32:d32) I can't tell how I would provide that 5v to the board itself - there doesn't seem to be a 5v in pin?