Wireless charging circuit design using 7~10V input

[tcmtech]

Once again the subject of why people make terrible power sources gets a work over.

 

[SujithZis]

Depends how many days you plan on running non-stop to charge the battery!
I assume that's the peak voltage/current. That's 50 uW, i.e. it's about 3 times better than the PVDFs quoted above. So it would only take 1/3 of the time estimated above to charge the battery, i.e. about 178/3 = 59 days of running! That figure doesn't account for self-discharge of the battery, or use of the phone.

I just want it for a project demonstration for now .... i have to somehow show it working

what if i connect those peizo discs in series .How much Volt and Ampere output will i get

how much power does a mobile charger require ... THE FACT being i just need the phone to charge for 5 minutes

 

[alec_t]

what if i connect those peizo discs in series .How much Volt and Ampere output will i get

According to your figures "In the peizo film that im using im getting 2.5V 0.02 mA per step ON ......... ONE PEIZO". That's a peak of 50 uW, so multiply that by the number of piezos then assume the average output is, say, 25% of that (it may well be less).

how much power does a mobile charger require

It varies from one charger to another. I have an old one here; the label says it's rated at 5.2V 400mA, i.e. 2.8W.

 

[audioguru]

I wish a Moderator will merge the two threads about this project.
In the other thread I wondered, "How on Earth will you mount the piezo transducers in a shoe so that they flex (bend) and unflex with each footstep without fracturing?"

Don't forget that a footstep energizes the transducers for only a moment. The energizing action might occur maybe 5% of the total time. If 100 footsteps are made in 1 minute then the 50uW of power is produced for a total of only 3 seconds. Use some simple arithmetic to calculate walking for months or years (without stopping) to charge the phone for 5 minutes.

Maybe you can cheat a little? Show that the phone is charging but at the extremely low current. But there is not enough current to light an LED to show that it is charging.
Or ask your teacher if you can change the requirements to have the energy harvested to operate a low power digital LCD watch.

 

[tcmtech]

If you are looking for a way to charge a cell phone in any reasonable time frame modifying a common LED type hand crank flashlight to have a stable 5 VDC output.
That is the most reasonable and cost effective method you will get to produce electrical energy from human input power that meets the minimum requirements to start to charge a cell phone.

Personally that is not a new idea either. In fact the tech has been around long enough now that hand crank USB port equipped charger/flashlights are around $3 - $15 to purchase depending on what output power capacity you need.