Hi all, this is my first post on what looks like a very interesting website. i have already read the other posts on this subject but haven't found what i am looking for.. so its time to start a thread.
what i am trying to build is is a complete system fitted in a plastic box where i can hook with a connector the cable coming from the dynamo, (the backlight takes its energy directly from the dynamo since it is already behind and has a circuit dedicated), has a usb charger output for a phone, so at least 500mA are needed, and when not charging any usb device (activated by switch) it should store the energy in a battery, from which i could later power a 9v radio which uses maximum 150mA.
i have tested my dynamo with just the voltmeter connected and the bike upsidedown and the max i reached was 27V. pedaling with the backlight on i got more or less 10V.
but i have read aound something regarding the dynamo being unloaded and how it affects its voltage.
i have already made a scheme from what i have learnt from other sites but i am sure there are a lot of mistakes.
View attachment 65010
for c1 i was thinking of using a few 470μF/35V hooked up in parallel (i got 4 from an old screen with all other caps, and if possible i would like to use as much of these as i can)
as for c2 it would be 0.1μF but i have seen it placed in parallel with c1 and with a value of 0.47μF, and other times in parallel with c3 as i have drawn, i must admit i dont fully understand the purpouse of this component. it is for stabilizing the current but why 2?
c3 instead i tought 22μF / 25V would be ok, a bit different from the original in the other circuit (22μF /16V) but at 16V i only have 100μF and 1500μF.
i still have serious doubts about the 9V part, and what type of battery to be used. ideally for size and weight a Li-ion battery would be perfect, but i have read that they will get damaged easily, and since they are so expensive it dosen't look like the solution.
the radio also works on lower voltagesalso 7.5V is great and that is the voltage the batteries
i found (no Li-ion at 9V) on farnell.com.
for the 5v voltage regulator i found this LM2940CT LDO
you can see it here
https://uk.farnell.com/national-semiconductor/lm2940ct-5-0/v-reg-ldo-5-0v-2940-to-220-3/dp/9490191
and the 9 volt
https://uk.farnell.com/national-semiconductor/lm2940t-9-0/ic-v-reg-ldo-9-0v-2940-to-220-3/dp/9493514
another important part is a led to indicate when the battery is fully charged but although really basic i woldn't know how to do it.
all corrections will be much appreciated, since like that i can understand better how this works!
actually thinking this straight , it will never be able to charge a 9v battery. what if i would get it to charge 3 AA batteries? the radio needs 6 of them so mabie charging 3 one day, 3 another, it could be possible to keep it running for long.. tell me what you think
what i am trying to build is is a complete system fitted in a plastic box where i can hook with a connector the cable coming from the dynamo, (the backlight takes its energy directly from the dynamo since it is already behind and has a circuit dedicated), has a usb charger output for a phone, so at least 500mA are needed, and when not charging any usb device (activated by switch) it should store the energy in a battery, from which i could later power a 9v radio which uses maximum 150mA.
i have tested my dynamo with just the voltmeter connected and the bike upsidedown and the max i reached was 27V. pedaling with the backlight on i got more or less 10V.
but i have read aound something regarding the dynamo being unloaded and how it affects its voltage.
i have already made a scheme from what i have learnt from other sites but i am sure there are a lot of mistakes.
View attachment 65010
for c1 i was thinking of using a few 470μF/35V hooked up in parallel (i got 4 from an old screen with all other caps, and if possible i would like to use as much of these as i can)
as for c2 it would be 0.1μF but i have seen it placed in parallel with c1 and with a value of 0.47μF, and other times in parallel with c3 as i have drawn, i must admit i dont fully understand the purpouse of this component. it is for stabilizing the current but why 2?
c3 instead i tought 22μF / 25V would be ok, a bit different from the original in the other circuit (22μF /16V) but at 16V i only have 100μF and 1500μF.
i still have serious doubts about the 9V part, and what type of battery to be used. ideally for size and weight a Li-ion battery would be perfect, but i have read that they will get damaged easily, and since they are so expensive it dosen't look like the solution.
the radio also works on lower voltagesalso 7.5V is great and that is the voltage the batteries
i found (no Li-ion at 9V) on farnell.com.
for the 5v voltage regulator i found this LM2940CT LDO
you can see it here
https://uk.farnell.com/national-semiconductor/lm2940ct-5-0/v-reg-ldo-5-0v-2940-to-220-3/dp/9490191
and the 9 volt
https://uk.farnell.com/national-semiconductor/lm2940t-9-0/ic-v-reg-ldo-9-0v-2940-to-220-3/dp/9493514
another important part is a led to indicate when the battery is fully charged but although really basic i woldn't know how to do it.
all corrections will be much appreciated, since like that i can understand better how this works!
actually thinking this straight , it will never be able to charge a 9v battery. what if i would get it to charge 3 AA batteries? the radio needs 6 of them so mabie charging 3 one day, 3 another, it could be possible to keep it running for long.. tell me what you think
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