Dynamo + Solar charging

Hi all, hope you are all well and safe in our recent times with covid.

I have a query.

I have a small hand dynamo with a 360 size brushed hobby motor attached and I know it will eventually burn out.
I understand about brushless technology and solar banks which I do not want to use as this is my project in mind.
I have the following batteries
Li-ion 3.7v 1800mah original in MP3 player.
NI MH 3.6v 900mah charges.
Li-ion 3.7v 10200mah charges.
I have a MP3 player board which has a built in 5v micro USB charging jack.
I also have SKU: CE05174, DC-DC USB 0.9V-5V to 5V DC Boost Step-up Power Supply Module.
I would like to charge one of these batteries from the hand dynamo and or a small solar panel.
I connected the dynamo to my MP3 circuit board which has a built in 5v micro USB charging jack without the battery or SKU: CE05174 then the led continually lit when I turned the dynamo handle normally.
When I turned it to fast the led died on the MP3.
I assume a part blew on the circuit board of my MP3 player because of not connecting SKU :CE50174 possibly.
I have spare MP3 player boards.
I watched YouTube and some people recommended a voltage regulator of 5v to protect from over current, a bridge connector so the dynamo can be wound clockwise or anti clockwise and possibly some diodes which I am not sure off for what purpose.
I understand it will take many hours to fully charge the battery by either way but the dynamo and solar panel is for occasional use and small topups away from power sources occasionally.
As I said previously, the MP3 player has a built in 5v micro USB charging jack.
I came to this site as there are positive reviews and recommendations about the knowledge and experience here.
If any one has any help it would be appreciated so I can order the correct parts to complete the project in lockdown, from core electronics.

Regards,
John.

2 Likes

Hi John, Welcome to the forum :smiley:

I’m not sure how many hand-cranks it takes to charge a battery but it’s definitely a cool experiment either way.
I would say some over-voltage protection is required but I’m not sure what would be best without knowing more about your dynamo. Do you have specs for the dynamo or the brushed motor that is used inside it?
Once we know more about what we are dealing with we will know what components to use to protect it.

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Hi Trent.
Thanx for the warm welcome.
Thanx for quick reply.
Here is the reference of the motor
No specs found for actual dynamo as it was given to me.
I updated the battery types I have and prefer to use the Ni-MH 3.6v 900mah battery.
Motor size is actually 360
Specs:
Operating range DC 2 to 8v
Nominal 3.6v

No load
Speed 5000rpm
Current 0.2A

Full load
Speed 4100rpm
Current 0.8A
Torque mN-m 3.9.
g-cm 40
Output 1.7W

Stall
Current 3.8A
Torque mN-m 23
g-cm 235

Reference above for using under DC power.
I connected the Ni-NH 3.6v 900 mah battery and it charges and red light goes out and works. Do you know if that is safe as the MP3 player only draws 3.7v and charges with 5v USB, I know I maybe asking too much.
I will be using by the hand dynamo so full load will be much less than specified.

Regards,
John

2 Likes

Hi John,

Calculating the voltage and power output of a brushed motor that is run in reverse is something I’ve known can be done, but I’d have to read up some more before I could do the math to calculate what you could expect to get out of it.

I can address some of your earlier questions though.

Your dynamo will produce a positive voltage if cranked one way, and a negative voltage if cranked the other. You can correct for this with a circuit called a bridge rectifier which is made up of diodes.
Here is a good entry-level tutorial to diodes which covers bridge rectifiers briefly:
https://learn.sparkfun.com/tutorials/diodes/all

For overvoltage protection you can also use a special type of diode called a zener diode, there is a good explanation of how they work and their use in overvoltage protection here:
https://www.rs-online.com/designspark/how-does-zener-diode-do-overvoltage-protection-in-circuit

2 Likes

Hi again.
Thanx for the swift reply.
Sorry forgot to mention do not know if this info is of use.
The MP3 board is 3w x 2 speakers 4ohms.
I will be only using 1 speaker out so mono.
Power source 3.7v battery, 5 volt micro USB in AC charging or powered.
I decided the bridge rectifier is not needed.
Do you have the suitable diodes in stock as would purchase approx 10 minimum and how much would be delivery to postcode 2166.
No great rush to reply.

Regards,
John

2 Likes

Hi John,

As for power or “rectifier” diodes, the 1n4001 is a popular choice

And as for the Zener diode, we’ve got one rated for 5.1V that might suit your application nicely:

All the best with your project, let us know if any other questions come to mind :slight_smile:
-James

2 Likes

Hi John,

I’m not sure I’m following what you mean by this.

Regarding shipping costs, you can estimate the cost of an order without having to put all the details into the checkout using the shopping cart. Once all the items you want are in the cart navigate to the shopping cart page, on the bottom left there will be an “estimate shipping” button, then you just need to enter a postcode and you will see the cost and delivery methods available based on the items in your cart.

2 Likes

Hi.
Thanks for the info I’ll order now.
Please let me know when the 5.1v diodes are back in stock.
Regards,
john

1 Like

Hi John,

Good luck with the build, if you want to be notified when an item comes back into stock there is a link on the product page you can use to get an automated email as soon as we have them again.

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To Core electronics.

Attention.
Thankyou Trent for all your support, I will click link for advise when back in stock,
Regards,

1 Like