PSU with variable AC input; overvoltage protection.

[Diy1995]

Just normal little silicon diodes, the 'standard' one is IN4148

Ok, thank you for your help.
So this would be it:
**broken link removed**

 

[Les Jones]

No.
1 When the alternator is producing 500 V RMS the peak of the waveform will be 707 volts. If you want to read this directly you need to scale the volatge down so it does not exceed 5 volts. With the above values the analogue input will see a peak of 7.94 volts if it was not clipped by the diode.). ( 707 x 5/445) Changing the atennuator values will solve this proble.
2 You will either have to synchronise the sampling with some point on the waveform or smooth the output of the rectifier so that the voltage does not change significantly over half a cycle of the waveform. The smoothing circuit will also cause some delay between the voltage from the alternator changing and the change being seen at the analog input. This will have to be taken into account in the control loop software.
3 As there is no isolation between the alternator output and the Arduino care will have to be taken that neither side of the alternator output can be connrcted to the Arduino earth.

Les.

 

[ronsimpson]

You have many problems. I will try to attack many of the problems.
You have 220vac most of the time but it could get as high as 500V. You need a 440V transformer but they are very hard to get and then there is price! I think we should use two 220V transformers. The transformers adds isolation and reduces the voltage down to some thing you can measure safely. I show using two full wave bridges. In this case 440V makes 16Vdc and 220 makes 8vcd. A switching power supply bucks down the (8 to 16V) down to 5Vdc. Now you need to divide 16V or maybe 20V max down to 5V. Because of the low voltage we don't need 1 watt resistors. (1/4 watt 1%) 15.0k and 4.99k will make 20V = 5V. By using the transformer(s) to reduce voltage many problems are solved. There will be some errors but I think this is a simple way.

You can series the primarys of the transformer and parallel the secondaries BUT you must get the phasing right or boom! By using two full wave bridge diodes the phasing is not a problem.

 

[awesomelumens]

I think I will use switch-mode regulator...
Precise zeners 5.1-5.3 volts of high wattage accompanied by a 1 amp fuse
Is this ment for overvoltage protection for analog input? thanks

Switch mode is best but its frequency sometimes disturbs and ripple comes in your way. So you need to be sure of its design and filter its output.y eah thats a simple solution as one of my regulators went bad and the led died by getting overvoltage. And another thing .... instead of messing with transformers why dont you use a voltage protector switch. It will allow voltages between 170-260approx. So when a surge is there it will help you.

 

[spec]

Hi DIY,

Below is a schematic for the off-line switch-mode power supply (SMPS) approach of post #4.

spec

​

LINKS
(1) Off-line switch-mode PSU: **broken link removed**
(2) 1N4148: https://www.vishay.com/docs/81857/1n4148.pdf
(3) Notional transformers: https://www.amazon.co.uk/s/?ie=UTF8...vtargid=kwd-6403662701&ref=pd_sl_6v1e3p8r76_b

 

[Diy1995]

I think that I will go with ronsimpson's version since i can get 16v transformers cheaper. I'm a student so I dont have much budged plus I have to invest in parts for my car, so price matters to me alot...
But there is no overvoltage protection for analog input right? So can I add two diodes in order to achieve this?

Thanks