Transformer-less power supply
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Hi,
Can I use a Capacitor-Resistor voltage dropper circuit without isolation to power up my Node like the one in below image.
I understand the node would not be mains isolated and would be a risk if touched. Apart from this are there any other risks or performance issues that I should be concerned of before I dive into constructing this circuit. I will add a LDO regulator at the output to get a regulated supply.
Please share your thoughts and views. Thanks
@Suresh-Mali I modified the above schematic, just to add some protection and regulation.
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@Suresh-Mali
I am currently working on reflashing a nrf51822 based smart socket to mySensors. The schematics were reversed-engineered by another guy, but it might be helpful to you as it
a ) transformer-less
b ) professionally tested (more or less)
https://habrastorage.org/files/2e9/76f/0b3/2e976f0b321e470a8d44a37717bc7098.jpg -
@Suresh-Mali
I am currently working on reflashing a nrf51822 based smart socket to mySensors. The schematics were reversed-engineered by another guy, but it might be helpful to you as it
a ) transformer-less
b ) professionally tested (more or less)
https://habrastorage.org/files/2e9/76f/0b3/2e976f0b321e470a8d44a37717bc7098.jpg@Toyman said in Transformer-less power supply:
@Suresh-Mali
I am currently working on reflashing a nrf51822 based smart socket to mySensors. The schematics were reversed-engineered by another guy, but it might be helpful to you as it
a ) transformer-less
b ) professionally tested (more or less)
https://habrastorage.org/files/2e9/76f/0b3/2e976f0b321e470a8d44a37717bc7098.jpgEven if you take a tested product and reverse-enginner it it's not tested and approved any longer when you build it yourself.
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Despite the security (which of course is the most important aspect here), such kind of circuit usually consumes from 2 to 10w (depending on AC voltage and C1 value), no matter in standby or not. I did some testing in the past and at end I dropped in favor of hi-link and similar small PSUs.
Home Assistant / Vera Plus UI7
ESP8266 GW + mySensors 2.3.2
Alexa / Google Home -
Despite the security (which of course is the most important aspect here), such kind of circuit usually consumes from 2 to 10w (depending on AC voltage and C1 value), no matter in standby or not. I did some testing in the past and at end I dropped in favor of hi-link and similar small PSUs.
@rvendrame My current design uses Hi Link 5V PSU, however I am looking at lowering the cost and this was one of the options.
I also reverse engineered some cheap 5v phone chargers, its an SMPS based design using single transistor. Are safe as there is isolation.
This might be my next option to look into. The problem is with the transformer. How do I get the transformer to my specification. Do I wind them myself? will have to look into it.
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You can find "Hi-link like" PSUs at Aliexpress for less than $2 USD. Not sure how less you can reach by producing them by yourself.
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myself already debate a little of this kind os tranformless power supply a few months ago.
here: https://forum.mysensors.org/topic/6927/3-3-or-5v-tranformer-for-mysensors-projects/11at the time i found how my zwavemodules worked.and that is the skematic:
It's tested by them and working on my house for more than 3 years and no problem.
the point that i reach is: doesn't worth build all this crap when a 2€ mini transformer do the same but safer.
i'm a arduino fan .Even sometimes don't undestanding how to use it :P
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myself already debate a little of this kind os tranformless power supply a few months ago.
here: https://forum.mysensors.org/topic/6927/3-3-or-5v-tranformer-for-mysensors-projects/11at the time i found how my zwavemodules worked.and that is the skematic:
It's tested by them and working on my house for more than 3 years and no problem.
the point that i reach is: doesn't worth build all this crap when a 2€ mini transformer do the same but safer.
@Tmaster Thanks for bringing this up. I was able to find LNK family ICs where I'll be able to source at cheaper price. I have ordered some LNK306 to test them. Cost me 80Rs/$1 and some cents. Will test once I receive them and post the results.
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@Suresh-Mali I modified the above schematic, just to add some protection and regulation.
@Suresh-Mali I recall from discussion back that using a Linear regulator like 7805 at the end of this sort of power supply is almost always a bad idea. Here every design use Zener for a reason. Zener will only dissipate heat when there is extra power available. Linear regulator will always dissipate power leaving less available power for your application.
