They are also cheep and most of them are certified to be safe.These days wall warts are very common for circuits that might have a little human contact
No R1 just takes the charge off the cap.1. one of my friend has suggested to install a 100 ohms in series with the AC input to limit inrush current! - Doesn't the bleeder resister (R1) do this ?
Yes it can over charge your battery.Can it make any harm to the battery? "
No R1 just takes the charge off the cap.
Yes it can over charge your battery.
No it won't! There will be a negligible change in the current because 230V is very much greater than 4V. The battery, when fully charged, will still have ~70mA forced through it and will probably overheat. That is one reason (apart from shock hazard) why this circuit is dangerous and shouldn't be built.However as we know, when the battery-charge go up (after 1-2 hours), the drain current from the source go down (<70mA).
Dear friends;
Thanks for the information and advices ! i really know this is very unsafe and very primary design. as well as i'm not going to build this. To be frank i just needed to get clarified some basic theory-parts from experts like u guys, by using this. Other than a few members, most of them were talking on the un-safety side of the diagram than useful theory matters.
However i have made some changes. Please see the attachment.
1. i put a full-wave bridge rectifier for pure DC
2. put a 1uF 450V Cap for extra safety
3. put a fuse at the main AC input
i have seen these type of re-chargeable torch are being widely used and sold in online markets like E-Bay!! And they are not too bad as it seen.
So please help me to understand following matters.
1. one of my friend has suggested to install a 100 ohms in series with the AC input to limit inrush current! - Doesn't the bleeder resister (R1) do this ? or is it necessary to put another one ?
2.what do you think on my main question: "Further, the Ni-Cad battery (3.6/700mA) will be charged with 4V/70mA source. However as we know, when the battery-charge go up (after 1-2 hours), the drain current from the source go down (<70mA). However, at the start, the charging current and the voltage was calculated according to “V=IR” and then a capacitor was selected in order to fulfill the above charging-values. So according to this argument, after 1-2 hours, charging voltage on the battery must be high than starting 4V (Ex; if I=30mA then voltage on the battery should go up to 134V). can this be happened ?? Can it make any harm to the battery? "
thanks for your time to write me.
best regards!
Kushan
Hello again,
So just to recap:
1. NiCd's and NiMH's might work ok with the charger at low enough currents (less than 200ma) with the zener and resistor addition, and a time limit on the charge and starting from zero charge.
2. Absolutely not to be used with Li-ion cells.
3. Shock hazard doesnt go away until the charger is unplugged from the wall so extreme caution is recommended.
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