Inductive charging mechanism: howto?
- Thread starter K-T
- Start date
Easiest way:
Get a pair of ferrite core halves from a flyback transformer, and fabricate a bobbin into the middle of each 'C' half. Wind about 300 turns of #30 magnet wire on each. Feed AC into one and mount it into the charger/base of your device, using some means of detecting when the device to charge is on the base (switch, photosensor, etc.). Connect the other to a rectifier bridge/filter/regulator/charge-circuit as needed and install it into the device in question. Then, design the two so that when the device is placed onto its base, the halves are accurately aligned with each other. If you make sure the gap is less than about 1/8", you should get adequate power transfer to be useful.
The downside of this is the efficiency loss when you're using what is essentially a split transformer. Plus, alignment of the two halves with each other will be crucial - most charge systems use pockets that force the device into the correct position to line everything up.
oO
Get a pair of ferrite core halves from a flyback transformer, and fabricate a bobbin into the middle of each 'C' half. Wind about 300 turns of #30 magnet wire on each. Feed AC into one and mount it into the charger/base of your device, using some means of detecting when the device to charge is on the base (switch, photosensor, etc.). Connect the other to a rectifier bridge/filter/regulator/charge-circuit as needed and install it into the device in question. Then, design the two so that when the device is placed onto its base, the halves are accurately aligned with each other. If you make sure the gap is less than about 1/8", you should get adequate power transfer to be useful.
The downside of this is the efficiency loss when you're using what is essentially a split transformer. Plus, alignment of the two halves with each other will be crucial - most charge systems use pockets that force the device into the correct position to line everything up.
oO
FreeBSDboy
Newly Enlightened
You might want to do some experimenting with different loop configurations. If you want, you could probably wind it such that it charges inductively and steps down in one step. That way you could eliminate parts on the charger side.
Also, realize that you are going to need a citcuit inside your light to rectify the AC current from your inductive pickup into DC for charging the light.
Also, realize that you are going to need a citcuit inside your light to rectify the AC current from your inductive pickup into DC for charging the light.
MrAl
Flashlight Enthusiast
Hello there,
In addition to the above ideas, i'd like to mention
that the core halves should actually touch if possible.
This increases efficiency overall. The two faces
can be painted, but the closer they come to each other
the better.
Take care,
Al
In addition to the above ideas, i'd like to mention
that the core halves should actually touch if possible.
This increases efficiency overall. The two faces
can be painted, but the closer they come to each other
the better.
Take care,
Al
I guess Klaus is on to the **very smart charger** for his next MR16 beasty - LOL - cool idea !
Some basic discussion regarding a fast charge circuit for exactly this type of lightsaber using high power MR16 bulbs and 12x multiples of AA NiMh cells in Mag xD bodies came up on the Decostar thread.
Might I invite you pros (you know who you are) to have a peek ? I´m still using the old TEA1101 but the newer TEA1102 can also charge SLA and LiIon and especiall the added LiIion capacility might be of interest too. I´m still dreaming of a CPF fast-charger DIY project like the ZLT in the old days - any interst ?
TIA
Klaus
Here´s a copy of my post in that other thread - sorry Klaus to capture your thread but I think its quite related - I mean adding your idea would make it soo much more elegant.
Charger discussion
[ QUOTE ]
Rothrandir said:
whould your charging mechanism work for 12 2100mah nimhs or 1000mah nicads in series? - 50w 10degree irc,
[/ QUOTE ]
Shure will - for some charger basics you might consider going through my old threads - short on time and too lazy to rewrite everything - sorry.
But just for short: To charge a string of cells you need around 1.5 to 1.6V x N where N is the number of cells - so 12 x 1.5 ~ 18V - it alwas can be a bit more so 20V is fine and will still work (I think) when using a smart charge circuit which drops a bit voltage too.
When using just a DC power source you basically just connect the source to your string of cells and either need to limit the current properly or your power supply does this on his own - just measure it when hooking up empty cells which draw the most current as the internal, resistance is lowest then. Don´t charge with more than the actual max capacity of your cells (this is named 1C) or around 1.2C to make up for some loss -this would be around 2.1A to 2.3A for your 2100mah cells. When using no smart charging circuit you need to be VERY careful not to overload the cells in monitoring cell voltage and/or temperature rise - plenty of good reads on the web for in-depths of this.
This is a poor-mans charger design which works quite well - but after you ruined some of your expensive high-cap NiMh cells you certainly will consider adding a smart-charge circuit. Some other notes on this: Using NiCds is less critical for overcharging them - using whichever (NiMh / NiCd) its also less critical to use C/10 charging currents - in this case you charge with just arounf 1/10 of the cells capacity but charge for around 12 hours - this greatly reduces the risk of overcharging the cells. Without a smart charger you always need to discharge the cells properly so you have a reference point to calculate your proper charge time.
I later added a DIY smart charge circuit based on the older TEA 1101 chip - after some modification - (from which my self-proclaimed nickname of IC slaughterhouse champ rooted as I burned up a truckload of those chips befor I found the right way to modify the circuit not only to accept 12 instead of 10 cells which was quite easy but to charge at a max rate of 4A instead of 1A - which was quite a challence) this circuit is working quite nicely. This DIY kit is only available in germany AFAIK so I have no good idea for you guys in the US on this. I´m shure there should be DIY smart charge circuit around on the web somewhere and initially I tried to create some CPF project on such a smart charger but was left mostly on my own on this - but still with more people joining in on such a project and others too realizing the benefit of in-flashlight charging this might get some more input and discussion ? I´m very much willing to share what I did so far .....
Besides the newer ref of this chip, the TEA1102, will also charge SLA´s and LiIons - so a CPF project DIY smart charger for NiMH, NiCd, SLA and LiIons at approx 10 USD cost might be some nice future project IMO. I can jump-start things with some reference design for the TEA1102 from Philips - but my DIY ability and electronic design capability is hmmmm less then it sometimes seems (as prooven by my nickname) - so other people would need to chim in.
But back to the charger issue - so basically there are some low cost choices and some "smarts" can be added too.
Summary:
Any >20V AC charger as often found with external modems can be modified to DC output using just a bridge rectifier (I only kind of remember the name) needs to be used - just a 1-2 USD part actually. Just this and just measure what current flows with empty cells - if too much just add a resistor until you reach the proper max current. On one design I aded a switch to add another resistor to choose betwen 1C and C/10 currents for 1hour gast charge and 10 hou slow charge.
For added nicety and security add a smart charge circuit - either DIY or bought off-the-shelf - the power source still has the same specs / needs - possibly you need slightly higher Vin when the circuit drops to much by itself.
Another low-cost power supply was found in the low-voltage halogen area (wehere the Mr16 comes from too) - there are 24V AC power supplies for that purpose which like above can be easily modified to DC - again here the higher volume makes these quite cheap.
The latest and best seems those Notebook power supplies - look for 50W + and 20V+ DC and you are set for a start - hopefully we can add a nice DIY CPF smart charger anytime soon.
And if you want to use a 50W IRC bulb I **guestimate** using 12A or AA cells at 2100ma will in theory give you 1/2h runtime but the voltage drop will be too high resulting in too low coltage and a yellow bad beam. You would be running the cells at 2C which the NiMhs can supply but only at a too high drop for satisfying results. Using 12 cells I still consider ~20W/25W to be max and if you want 35W or 50W bulbs either go with 12x2 cells or higher cap cells like C/D, or NiDs cells which have a lower voltage drop by design - or go with the RC cells which should have a lower voltage drop too. There are developments of high-drain NiMh cells but I haven´t followed this recently. There also will be differences between different NiMhs cells too - my favored Sanyo cells do seem to show a higher-than average voltage drop so possibly using other cells you might get a better result and a 35/50W bulb might run OK - but I would doubt it.
Oh and as was mentioned there are nice chargers on the market which can supply high currents with a dial for the number of cells (while 12 is kind of exotic) and nice bells and whistles typically out of the RC area - but if those would met all criteria described above they would run quite high in price and I personally didn´t wanted to spent that much.
DIY Charge circuit - german only
TEA1102 Data Sheet with test circuit
And there seem to be a bunch of ICs too from the same companies where most of the LS driver circuit ICs are coming from and it **seems** to me that the charger circuits are not too much different from the driver circuits - but again I´m not the right person to design such.
Oh my - again too much typing already ...... sorry for the typos
Klaus
Some basic discussion regarding a fast charge circuit for exactly this type of lightsaber using high power MR16 bulbs and 12x multiples of AA NiMh cells in Mag xD bodies came up on the Decostar thread.
Might I invite you pros (you know who you are) to have a peek ? I´m still using the old TEA1101 but the newer TEA1102 can also charge SLA and LiIon and especiall the added LiIion capacility might be of interest too. I´m still dreaming of a CPF fast-charger DIY project like the ZLT in the old days - any interst ?
TIA
Klaus
Here´s a copy of my post in that other thread - sorry Klaus to capture your thread but I think its quite related - I mean adding your idea would make it soo much more elegant.
Charger discussion
[ QUOTE ]
Rothrandir said:
whould your charging mechanism work for 12 2100mah nimhs or 1000mah nicads in series? - 50w 10degree irc,
[/ QUOTE ]
Shure will - for some charger basics you might consider going through my old threads - short on time and too lazy to rewrite everything - sorry.
But just for short: To charge a string of cells you need around 1.5 to 1.6V x N where N is the number of cells - so 12 x 1.5 ~ 18V - it alwas can be a bit more so 20V is fine and will still work (I think) when using a smart charge circuit which drops a bit voltage too.
When using just a DC power source you basically just connect the source to your string of cells and either need to limit the current properly or your power supply does this on his own - just measure it when hooking up empty cells which draw the most current as the internal, resistance is lowest then. Don´t charge with more than the actual max capacity of your cells (this is named 1C) or around 1.2C to make up for some loss -this would be around 2.1A to 2.3A for your 2100mah cells. When using no smart charging circuit you need to be VERY careful not to overload the cells in monitoring cell voltage and/or temperature rise - plenty of good reads on the web for in-depths of this.
This is a poor-mans charger design which works quite well - but after you ruined some of your expensive high-cap NiMh cells you certainly will consider adding a smart-charge circuit. Some other notes on this: Using NiCds is less critical for overcharging them - using whichever (NiMh / NiCd) its also less critical to use C/10 charging currents - in this case you charge with just arounf 1/10 of the cells capacity but charge for around 12 hours - this greatly reduces the risk of overcharging the cells. Without a smart charger you always need to discharge the cells properly so you have a reference point to calculate your proper charge time.
I later added a DIY smart charge circuit based on the older TEA 1101 chip - after some modification - (from which my self-proclaimed nickname of IC slaughterhouse champ rooted as I burned up a truckload of those chips befor I found the right way to modify the circuit not only to accept 12 instead of 10 cells which was quite easy but to charge at a max rate of 4A instead of 1A - which was quite a challence) this circuit is working quite nicely. This DIY kit is only available in germany AFAIK so I have no good idea for you guys in the US on this. I´m shure there should be DIY smart charge circuit around on the web somewhere and initially I tried to create some CPF project on such a smart charger but was left mostly on my own on this - but still with more people joining in on such a project and others too realizing the benefit of in-flashlight charging this might get some more input and discussion ? I´m very much willing to share what I did so far .....
Besides the newer ref of this chip, the TEA1102, will also charge SLA´s and LiIons - so a CPF project DIY smart charger for NiMH, NiCd, SLA and LiIons at approx 10 USD cost might be some nice future project IMO. I can jump-start things with some reference design for the TEA1102 from Philips - but my DIY ability and electronic design capability is hmmmm less then it sometimes seems (as prooven by my nickname) - so other people would need to chim in.
But back to the charger issue - so basically there are some low cost choices and some "smarts" can be added too.
Summary:
Any >20V AC charger as often found with external modems can be modified to DC output using just a bridge rectifier (I only kind of remember the name) needs to be used - just a 1-2 USD part actually. Just this and just measure what current flows with empty cells - if too much just add a resistor until you reach the proper max current. On one design I aded a switch to add another resistor to choose betwen 1C and C/10 currents for 1hour gast charge and 10 hou slow charge.
For added nicety and security add a smart charge circuit - either DIY or bought off-the-shelf - the power source still has the same specs / needs - possibly you need slightly higher Vin when the circuit drops to much by itself.
Another low-cost power supply was found in the low-voltage halogen area (wehere the Mr16 comes from too) - there are 24V AC power supplies for that purpose which like above can be easily modified to DC - again here the higher volume makes these quite cheap.
The latest and best seems those Notebook power supplies - look for 50W + and 20V+ DC and you are set for a start - hopefully we can add a nice DIY CPF smart charger anytime soon.
And if you want to use a 50W IRC bulb I **guestimate** using 12A or AA cells at 2100ma will in theory give you 1/2h runtime but the voltage drop will be too high resulting in too low coltage and a yellow bad beam. You would be running the cells at 2C which the NiMhs can supply but only at a too high drop for satisfying results. Using 12 cells I still consider ~20W/25W to be max and if you want 35W or 50W bulbs either go with 12x2 cells or higher cap cells like C/D, or NiDs cells which have a lower voltage drop by design - or go with the RC cells which should have a lower voltage drop too. There are developments of high-drain NiMh cells but I haven´t followed this recently. There also will be differences between different NiMhs cells too - my favored Sanyo cells do seem to show a higher-than average voltage drop so possibly using other cells you might get a better result and a 35/50W bulb might run OK - but I would doubt it.
Oh and as was mentioned there are nice chargers on the market which can supply high currents with a dial for the number of cells (while 12 is kind of exotic) and nice bells and whistles typically out of the RC area - but if those would met all criteria described above they would run quite high in price and I personally didn´t wanted to spent that much.
DIY Charge circuit - german only
TEA1102 Data Sheet with test circuit
And there seem to be a bunch of ICs too from the same companies where most of the LS driver circuit ICs are coming from and it **seems** to me that the charger circuits are not too much different from the driver circuits - but again I´m not the right person to design such.
Oh my - again too much typing already ...... sorry for the typos
Klaus
ab
Enlightened
A short one here - inductive charger: cordless toothbrush. These are inexpensive and designed exactly to do what we are discussing here. The Braun units are now quite inexpensive. (or you could just get one from a yard sale where they seem to pop up from time to time...)
Lots of inductive charging fun!
/ubbthreads/images/graemlins/smile.gif
A.
Lots of inductive charging fun!
/ubbthreads/images/graemlins/smile.gif
A.
Thank you guys for all the information.
Klaus, lots of useful information in your post - and you are right. I came up with this (what might be a nice idea for the MR16 project) charger while watching these Braun electric tooth brushes. /ubbthreads/images/graemlins/rolleyes.gif
I will have to carefully read through your additional posts. /ubbthreads/images/graemlins/wink.gif
Klaus, will contact you on the DIY CPF charger project in the next days (it must have soemthing to do with the name coincidence! /ubbthreads/images/graemlins/grin.gif)
Klaus. /ubbthreads/images/graemlins/icon15.gif
Klaus, lots of useful information in your post - and you are right. I came up with this (what might be a nice idea for the MR16 project) charger while watching these Braun electric tooth brushes. /ubbthreads/images/graemlins/rolleyes.gif
I will have to carefully read through your additional posts. /ubbthreads/images/graemlins/wink.gif
Klaus, will contact you on the DIY CPF charger project in the next days (it must have soemthing to do with the name coincidence! /ubbthreads/images/graemlins/grin.gif)
Klaus. /ubbthreads/images/graemlins/icon15.gif
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