VapCap DIY Induction Heating : Bits 'n' pieces

[stardustsailor]

Well,although @Pipes has made an awesome thread about IH ,
I thought ,oh well ,multiple brains are better than a single one
when it comes to the evolution of an idea .
So here we are !
At this thread all sorts of trivia about IH can be posted .
Helpful information ,tips'n' tricks ,mods ,alternative designs ,microcontroller hardware and software ,etc.


So ,let's start .

The 5~12v ZVS Induction Heating Power Supply Module ,
is the cheapest ,simplest and easiest to obtain IH driver .
It can be found on E-bay ,Bang-Good ,Fastech ,Aliexpress,Amazon ,Sainsmart,Walmart
and at quite few other web -markets .

First thing for the brave DIYer is to check the polarity of the diodes VD1 & VD2 ,as
also the polarity of the two Zener diodes DZ1 & DZ2 .
Some of these drivers have not been under QC ,thus you should check the polarity
of these four diodes ,before assembling & powering the IH device .

DZ1 & DZ2 have a blue line indicating the cathode
( aka "minus side/pole " aka " to ground " or " to GND " aka " to 0V " ) .
Same with VD1 & VD2 ,which have a grey/white line .
At DZ1 & DV1 the cathode side should be facing towards the "JP1 " power connection post .
At DZ2 & VD2 the cathode is inverted ,facing the " +IN " power connection post .

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

These drivers can fry their two MOSFETS quite easily ,
due to low battery voltage ,bad coil installation ,rapid ON/OFF cycles ,etc .

The original MOSFET is the 30N06 ( 32 A ,60 V ) N-channel power MOSFET.

Datasheet :
https://cdn.sparkfun.com/datasheets/Components/General/FQP30N06L.pdf
http://www.unisonic.com.tw/datasheet/30N06.pdf
https://gr.mouser.com/datasheet/2/196/Infineon-IPD30N06S2L_13-DS-v01_00-en-1226066.pdf
Source :
https://gr.mouser.com/ProductDetail/Infineon-Technologies/IPD30N06S2L13ATMA4?qs=sGAEpiMZZMshyDBzk1/Wi%2bcEGIVrBqg7d7tRVdUCWI3CHJrx/iMcrg==

But other N-channel power FETs can be used instead of the 30N06 .
Some replacement examples :
IRF540N ( 33 A ,100 V ) A really "tough" FET ! :
https://www.infineon.com/dgdl/irf540n.pdf?fileId=5546d462533600a4015355e396cb199f

IRFP260N ( 50A ,200V ) Most probably the best alternative.A real work-horse ! :
https://www.infineon.com/dgdl/irfp260n.pdf?fileId=5546d462533600a4015356289dcf1fe2
https://www.vishay.com/docs/91215/91215.pdf

IRFZ44 ( 50A ,60 V ) Very close specs to the 30N06,
but somewhat a better FET than the latter :
https://www.vishay.com/docs/91291/91291.pdf

@Pipes uses the NTD4806N ( 76 A , 30 V ) with great results ! :
https://www.onsemi.com/pub/Collateral/NTD4806N-D.PDF

 

[stardustsailor]

Zero Voltage Drop Reverse Polarity Protection for 12V 10 A BMS .

Sometimes the simplest solution is actually the best !



Just two small & cheap parts needed !

When the polarity is correct the Schottky diode is effectively canceled from the active circuit,
while the fuse acts as a conductor.No power loss & zero voltage drop .

If ALL the batteries are installed backwards ,then the schotkky diode conducts
and the fuse trips .

The rated amperage of both the Schotkky diode and breaker /fuse should be chosen accordingly to the operating and max output current of the battery cells.

For 25-30 A max operating current battery cells ,
the fuse should be 20A ( 5 to 10 Ampere lower than max ) .

https://www.waytekwire.com/item/46853/TE-Connectivity-BD280-1130-20-16-Resettable-Fuse/

https://www.waytekwire.com/datasheet/46853.pdf

http://www.farnell.com/datasheets/2...Joq0XlLGN3FiCdXbC_tUKkiS_8vPrQYxoCS2EQAvD_BwE



EDIT : The circuit has not been verified as fully operational .
If it fails to work ,then the same ' Schotkky-Fuse/Breaker ' protection combo
like at pad " B+" should be installed also at pads " B1 " & " B2 " ,
as shown at the following schematic .
This way it serves as a Reverse Polarity Protection for the BMS module ,
but also serves as an Over -Current Protection for the Li-ion battery cells .

 

[stardustsailor]

Alternative ON/OFF switch for battery powered IH models.

Li-Ion battery cells should not be charged while being used .
If opposite ,then it has a really deteriorating effect on their service life ,
due to elevated temperature and to prolonged high charge voltage.**

Wired this way ,when the IH is switched ON , a plugged charger will have no effect.
It will not charge the batteries .
The IH device can only be charged when it is switched OFF .

It needs a Single pole / Double Throw switch ( SPDT ) with a rating of more than 10 A / 12 VDC.






** ( ...)
Li-ion cannot absorb overcharge. When fully charged, the charge current must be cut off. A continuous trickle charge would cause plating of metallic lithium and compromise safety. To minimize stress, keep the lithium-ion battery at the peak cut-off as short as possible.

Once the charge is terminated, the battery voltage begins to drop. This eases the voltage stress. Over time, the open circuit voltage will settle to between 3.70V and 3.90V/cell. Note that a Li-ion battery that has received a fully saturated charge will keep the voltage elevated for a longer than one that has not received a saturation charge.

When lithium-ion batteries must be left in the charger for operational readiness, some chargers apply a brief topping charge to compensate for the small self-discharge the battery and its protective circuit consume. The charger may kick in when the open circuit voltage drops to 4.05V/cell and turn off again at 4.20V/cell. Chargers made for operational readiness, or standby mode, often let the battery voltage drop to 4.00V/cell and recharge to only 4.05V/cell instead of the full 4.20V/cell. This reduces voltage-related stress and prolongs battery life.

Some portable devices sit in a charge cradle in the ON position. The current drawn through the device is called the parasitic load and can distort the charge cycle. Battery manufacturers advise against parasitic loads while charging because they induce mini-cycles. This cannot always be avoided and a laptop connected to the AC main is such a case. The battery might be charged to 4.20V/cell and then discharged by the device. The stress level on the battery is high because the cycles occur at the high-voltage threshold, often also at elevated temperature.

A portable device should be turned off during charge. This allows the battery to reach the set voltage threshold and current saturation point unhindered. A parasitic load confuses the charger by depressing the battery voltage and preventing the current in the saturation stage to drop low enough by drawing a leakage current. A battery may be fully charged, but the prevailing conditions will prompt a continued charge, causing stress.
(...)

https://batteryuniversity.com/index.php/learn/article/charging_lithium_ion_batteries

 

[stardustsailor]

A cheap digital Voltmeter as a battery gauge

These can be found in two versions:

The two wire version ( Red & Black wires )
https://www.ebay.com/itm/0-28-Digital-Voltmeter-Panel-DC-2-50-30V-Voltage-Mount-LED-Voltmeter-Red-Useful/122640526223?hash=item1c8df1eb8f:g:7D8AAOSwqv9V7O2G&_sacat=0&_nkw=panel+mount+digital+voltmeter&_from=R40&rt=nc&_trksid=m570.l1313


and the three wire version (Red ,White & Black wires )
https://www.ebay.com/itm/0-100V-Voltmeter-Digital-LED-0-36-Display-Panel-Mount-3-Wires-DC-Voltage-Tester/112626404612?hash=item1a390e8d04:m:mC8WkldOE46EhAUm4PBgBAw&var=413059084337&_sacat=0&_nkw=panel+mount+digital+voltmeter&_from=R40&rt=nc&_trksid=m570.l1313

For the three wire version ,
the white wire should be shorted ( connected ) with the red wire ,
for our application .

Tip : A toggle or momentary switch or a push button can be connected in line
with the voltmeter in case we do not want /need for the voltmeter to stay ON at all times
( Digital Voltmeter power : 0.24 to 0.18 Watts depending on the 7-seg LED color )

At the following schematic ,the Voltmeter is installed as an " IH ACTIVE " indicator.
As the push button S2 is pressed the IH module is powered ,as also the Voltmeter.
While the VapCap is being heated ,the actual voltage of the 3S Li-ion battery pack
can be viewed
( there is a minor Voltage drop ,due to wiring ,soldering ,connectors,switches,etc.
To minimize that voltage drop at the 12 V-10A power line,
wiring should be kept as short and as thick (diameter wise )
as possible ,there must not be any cold solder joints and the wires should be tightly
connected to any connectors/plugs/sockets and/or screw-posts. )



For the 3S Li-ion pack :

100% charge : Voltmeter indication = 12.6 V
90% charge : Voltmeter indication = 12.45 V
80% charge : Voltmeter indication = 12.3 V
70% charge : Voltmeter indication = 12 V
60% charge : Voltmeter indication = 11.7 V
50% charge : Voltmeter indication = 11.4 V
40% charge : Voltmeter indication = 11.1 V
------------- ! Charge ! -------------------
30% charge : Voltmeter indication = 10.8 V
20% charge : Voltmeter indication = 10.5
10% charge : Voltmeter indication = 9 V

Caution ! If the batt-pack's voltage drops below 10.8 V
the IH device should not be used any further and the batt-pack should be recharged .

 

[elykpeace]

So much great info
Thanks @stardustsailor something to mess with this weekend

 

[stardustsailor]

Connecting an ordinary ( epoxy encapsulated ) LED at 12 VDC




Direct :

For directly powering a small ordinary LED with 12 VDC ,
a 1000 Ohm ( 1K ) ressistor has to be connected in
series with the LED ,as a current limiter .Those small LEDS usually draw 20 mA each.
R = V / I .
Since we need the current to be 20mA or less at 12 VDC ,then R = 12 / 0.02 = 600 Ohm.
Connecting a larger resistor than 600 Ohm to limit the current ,we minimize the
chances of the LED getting fried in case of over-voltage / power surges / spikes .

The led can be controlled ( switched ON/OFF )
with a mechanical or digital switch , a relay ,a 12 VDC IC output ,etc.

---------------------------------------------------------------------------
---------------------------------------------------------------------------
TTL controlled :

If the power line is still 12 VDC but we need to control the switching of the LED ,
with a microcontroller output signal aka TTL ( Transistor - Transistor Logic **)
with Vcc being 5 VDC (when on HIGH state ) ,
then we need a BC547 NPN transistor and two resistors .
One is the 1K current limiter for the LED and the other is the 10K Base resistor of the transistor.
This resistor will ensure that the transistor will behave as a simple switch
(only ON & OFF states ,no signal amplification ) with no power losses .

https://www.electronicshub.org/transistor-as-switch/

https://www.electronics-tutorials.ws/transistor/tran_4.html

https://components101.com/bc547-transistor-pinout-datasheet

https://www.sparkfun.com/datasheets/Components/BC546.pdf

https://www.arduino.cc/documents/datasheets/BC547.pdf

**(...)
Standard TTL circuits operate with a 5-volt power supply. A TTL input signal is defined as "low" when between 0 V and 0.8 V with respect to the ground terminal, and "high" when between 2 V and VCC (5 V),and if a voltage signal ranging between 0.8 V and 2.0 V is sent into the input of a TTL gate, there is no certain response from the gate and therefore it is considered "uncertain" (precise logic levels vary slightly between sub-types and by temperature). TTL outputs are typically restricted to narrower limits of between 0.0 V and 0.4 V for a "low" and between 2.4 V and VCC for a "high", providing at least 0.4 V of noise immunity (...)

https://en.wikipedia.org/wiki/Transistor–transistor_logic

 

[stardustsailor]

" Portside " Revisited : Glass Tube Support


I'm in the process of making my own "Portside " IH device.
I'm still waiting for the most parts to arrive ,though.
Meanwhile,I can work with what I'm currently having .

So ,I got to do a rough design on how the glaas tube is going to be supported inside the
" Portside " case .


Used a piece of thick FR4 pcb as a base plate
( left the copper film intact as well as the - "burned " / light exposed photosensitive lacquer )
and then machined a Polyamide #6 20 mm Dia.rod into a glass tube base ,
with 2x O-ring grooves ( #109 ) for the glass tube to firmly attach .











-------------------------------------------------------------------------------------------
https://www.fasttech.com/products/3051/10020979/5236300

https://www.banggood.com/Aluminum-P...-p-982711.html?rmmds=myorder&cur_warehouse=CN

http://www.oringsandmore.com/silicone-o-rings-size-113-price-for-25-pcs/

http://www.oringsandmore.com/silicone-o-rings-size-109-price-for-50-pcs/

 

[stardustsailor]

Checking the accuracy and the operating power of
the 3-wire digital (7seg Blue LED ) Voltmeter .





Verdict : Accurate enough for Li-ion battery gauge
and it dissipates only ~ 100 mWatts ( 0.1 W ) .
Great for the job !

https://www.ebay.com/itm/DC-0-30V-3-Wire-LED-Digital-Display-Panel-Volt-Meter-Voltage-Voltmeter-Car-Motor/173021758827?hash=item2848e6856b:m:mE9kFIUxTbOrYhZ7rx68pJA&var=471790882827&_nkw=3+wire+digital+voltmeter&rt=nc

 

[Ramahs]

I'm definitely watching this thread!

 

[stardustsailor]

Automatic Input Power selection .

An "automated" version of the
"Alternative ON/OFF switch for battery powered IH models " mod.

All it needs is a Double Pole -Double Throw ** 12 VDC relay , rated 10A or 12 A
and two diodes : 1x 1N4148 and 1x 1N4001 .

--------------------------------------------------------------------------------------
**
Double Pole means that the relay can switch ON /OFF two separate & isolated from each other lines / ways ,like having two different switches .

Double Throw means that each of those "switches " have 3 contacts
instead of the classic two .

The middle pin is the " wiper " ,the moving contact of the relay .
One of the remaining two pins is the relay contact that the wiper rests
( thus connecting with ) while the relay is not activated .
This is called " Normally Closed " / NC ( because it closes a circuit ) .

The other one is called " Normally Open " / NO
and the wiper will short /connect with that contact ,once the relay is activated .
At the schematic inside the gray rectangle ( DPDT relay ) :
Marked as 1 & 2 are the input power pins of the relay ( + 12 VDC & GND )

C1 is the #1 switch wiper .
It rests at contact C2 ( NC ) while the realy is inactive
and as soon the relay is activated ,the wiper C1 contacts with C3 ( which is NO ) .

Same goes with the "switch #2 " and it's contacts : C4 ( wiper ) , C5 ( NC ) and C6 ( NO ).
-------------------------------------------------------------------------------------------
How the circuit operates :

If there is not a charger pluged ,the relay remains inactive.
So the contacts remain as in the schematic .
Starting from the BMS (as a power source ) from P+ ( as OUTPUT ),
power reaches the points C4 and C3.

C3 ( NO ) is a " dead end " / " blind point " ,since is not connected to any circuitry .

From C4 power moves to C5 ( NC relay contact ) and from there to the ON/OFF switch ,
allowing us to switch ON or OFF the IH device.

But in case a Li-ion Cell charger is plugged ,
power reaches the #1 power input of the relay and the relay is activated immediately .

Wiper C1 moves from C2 to C3 ,
as also wiper C4 moves from C5 to C6 .

C4 which was powering the MOSFET switch via the C5 contact ,
now it is contacting the "blind point " C6 contact .
The MOSFET switch as also the ZVS IH Driver are effectively
canceled - " thrown out " of the power line .
They can not be powered anymore .

Wiper C1 which is connected to + 12.6 VDC of the charger ,now is contacting C3 ,
which goes to P+ ( as INPUT ) of the BMS ,thus charging the batteries .
----------------------------------------------------------------------------------------
The 1N4001 diode is there to drop the 12.6 VDC from the Li-ion charger to ~ 11.8 VDC ,
thus protecting the coil of the relay from overheating ,while the Li-ion cells are charging.

Caution :
The power line from charger to BMS must be 12.6 VDC ,so C1 has to be
connected to the DC charger socket before the 1N4001 diode -
as shown at the schematic .

The 1N4148 is a high speed diode and is protecting the charger from
inductive kickback currents from the relay's coil .

Optional : A resistor with a value of 1K ,
can also be connected in series with the 1N4148 diode ,
for taking the " kickbak inductive current" load and turn it into heat ,
otherwise that job is done by the relay coil,which has of course an impedance also.

https://www.vishay.com/docs/88503/1n4001.pdf
https://www.vishay.com/docs/81857/1n4148.pdf
______________________________________________________________________
______________________________________________________________________

Saving some trouble ,one of these can also be used :
https://www.ebay.com/itm/For-High-Low-Level-Trigger-5V-9V-12V-24V-1-2-4-Channel-Optocoupler-Relay-Module/142667560937?hash=item2137a637e9:m:m6rMvqwtwkQdh9aYffkJCIg&var=441651291256&_sacat=0&_nkw=2-Channel+12V/250V+AC+Relay+Module&_from=R40&rt=nc&_trksid=m570.l1313

" IN 1 " & " IN 2 " have to be connected /shorted with " DC + ",
and both jumpers should be at " HIGH " level trigger.

 

[stardustsailor]

A "Portside " at it's ..side .

The 100 mm x 100 mm surfaces in this version are " top cover " and " bottom of the case " .

 

[stardustsailor]

Induction Coil Thermal Protection .

Parts needed for the mod :

- Bimetallic disc thermostat -Normally Closed ( NC ) - 100°C ** :
https://www.ebay.com/itm/KSD9700-Bimetal-Disc-Thermostat-Thermal-Protector-250V-5A-40-135-centigrade/132643015215?ssPageName=STRK:MEBIDX:IT&var=431975311065&_trksid=p2057872.m2749.l2649

- Kapton tape :
https://www.ebay.com/itm/10mm-100ft-BGA-High-Temperature-Heat-Resistant-Polyimide-Gold-Kapton-Tape/252331950064?epid=584667196&hash=item3ac027fff0:g:ejAAAOSwoudW9Joe&_sacat=0&_nkw=capton+tape&_from=R40&rt=nc&_trksid=m570.l1313

- Baking paper ( very familiar to resin lovers ),one strip of 51 mm x 25 mm .


Schematic :

The NC passive thermostat is in series connected with the IH activating push button / tactile switch .
If the coils temperature exceeds 100°C then the bimetallic discs snap ,opening the circuit to the MOSFET
trigger.The IH driver is switched OFF ,until the coil temperature drops below 100°C .

How to attach the thermostat to the IH coil.

1 ) Wrap the coil with a round of baking paper ( 51 x 25 mm strip ) .
2 ) Now ,fully cover the baking paper ,by wraping with Kapton tape .One layer .
3 ) Place the thermostat at the middle of the coil's length.
4 ) Wrap around the thermostat with couple wrapping of Kapton .
Heat shrink tubing can also be used at this step,instead of wrapping with Kapton .
5 ) Connect one terminal of the thermostat to the Mosfet switch input " V+ " ,
while the other terminalo will be connected with the push button / tactle switch .

**
The most common magnetic wire insulating enamels are rated for 105°C .
That's why the chosen temp is 100°C .

http://www.ee.co.za/article/varnish-insulation-wire-enamels.html

EDIT /PS :
Just noticed the ON/OFF switch wiring of the schematic ...
When OFF the IH device can be charged then,
but also serves as a .. 12 V power bank !

 

[stardustsailor]

That's my final plan for an IH device .










- Thermal protection on the induction coil

- Kapton tape between glass tube and Induction coil ,
protecting magnetic wire enamel from vibrations / heat expansion-contraction movement

- Activation via momentary push button ( with LED indication )

- 7-seg numerical LED display cell voltage indication via momentary push button

- "Charge" - " OFF " - " ON " switch

- Fully cushioned glass tube ,installed on Polyamide #6 base and
" sandwiched " between silicone o-rings and case rubber grommet.

- Eddy current insulated induction coil

 

[stardustsailor]

PARTS LIST

ELECTRONIC MODULES :

1x 5-12 VOLT ZVS IH PSU + INDUCTION COIL

1x 3S BMS 12 VOLT - 10A MODULE (first 3S on the drop list )

1x 15A 400Watt MOSFET switch

1x 7seg DIGITAL VOLTMETER case/panel mount

1x 3S 1A Li-ion Battery Charger 12.6 Volt (choose EU or US plug ) : EU plug or US plug .

PASSIVE COMPONENTS :

1x ON-OFF-ON switch 125VAC / 10 A (up to ~30 VDC it can withstand the rated current )

2x Momentary push button with LED (Normally OPEN )

1x DC socket case/panel mount

1x 85° to 100°C bimetallic thermostat ( choose temp and the NC type )

2x 3 Pins Wire Connector Female Male ( for the push buttons )

BATTERIES :

3x Li-ION 18650 CELLS ( Rated for continuous current > 15 A )

1x 3S Battery holder

MISC :

1x Alum. case

1x Glass Tube ( Cloupor M3 ) 16 mm Dia. x 35 mm length .

5x #109 VMQ o-rings (for glass tube cushioning & attaching and cap heat insulation )

3x #113 VMQ o-rings (for induction coil protection )

1x 12 mm case/panel rubber grommet

Kapton tape

2m x Silicone -Glass Fiber braided wire sleeve

High Temp double sided tape

--------------------------------------------------------------------------------
And a custom -made base for the glass tube that can be made
out of 20 mm Dia hard wood rod ,or silicone ,or cork or
from synthetics like a POLYAMIDE #6 rod .

 

[stardustsailor]

Adjustable Resonance Induction Heater ( 12 V )




The resonance is selected :

Step #1 : The work coil and the cap bank ( at least 4x high frequency , low ESR from the MKP / MFP kind) will form a LC resonant circuit.Use a coil inductance online calculator and a LC online calculator to figure the inductance of work coil and the cap bank total capacitance needed for the chosen / wanted resonance frequency .

https://www.allaboutcircuits.com/tools/coil-inductance-calculator/
https://www.allaboutcircuits.com/tools/tank-circuit-resonance-calculator/

Step #2 : if the timing circuit of 50K pot ,10K resistor and 470pF cap will not cover the set resonance frequency of the Cap bank & work coil ( they cover from ~21 kHz up to 150 kHz resonance ) ,then their values have to be changed according to the following graph :

Step #3 : a small ferrite core inductor has to be placed in series
at the floating VS output line ,before the tank bank / work coil
and after the RC low-pass filter ,as a current limiter .
Calculate first it's impedance and then it's inductance ,
taking into account the Max operating current* of the work coil and the set resonance frequency :
https://www.allaboutcircuits.com/tools/coil-inductance-calculator/
http://www.learningaboutelectronics.com/Articles/Inductor-impedance-calculator.php
* For 10 A max current @ 12VDC, it's impedance should be 1.2R
ZL= 2πf L => L = 1.2 / ( 2π * resonance frequency )


- Optional #1 : The thermal protection shut-down circuit can be omitted .

- Optional #2 : The three RC low-pass bypassing filters
( 2x 10R 2W + 2.2nF 400V & 1x 4.7R 2W + 4.7nF 400V can also be omitted ,but it is not suggested .

- The two pairs of DC cut-off caps ( 2.2 uF ) can be rated of lower voltage ,100 V for example ,but not suggested.


https://www.infineon.com/dgdl/ir2153.pdf?fileId=5546d462533600a4015355c8c5fc16af

 

[stardustsailor]

Adjustable Resonance Induction Heater ( 12 V ) with TTL ( or CMOS ) PWM signal input
( from a microcontroller ,for example )





As the previous circuit ,but with a different MOSFET gate driver
( UCC2720x High Frequency, High-Side and Low-Side Driver )
and a single channel signal inverter
( MC74VHC1GT04 Inverting Buffer / CMOS Logic Level Shifter )
at the Low-side gate input signal ( LI ) in order to invert the High-side gate input signal ( HI ) ,allowing the use of a single input PWM TTL ( or CMOS ) signal .
The two 10K resistors are used to securely drop the signal to ground ( VDC ) ,
when LOW .

http://www.onsemi.com/pub/Collateral/MC74VHC1GT04-D.PDF

http://www.ti.com/lit/ds/symlink/ucc27200.pdf

** !!! CAUTION !!! Choose :

UCC27200 for CMOS input threshold
( HIGH : 3.5-5 VDC / LOW : 0 - 1.5 VDC )

OR

UCC27201 for TTL input threshold
( HIGH : 2-5 VDC / LOW : 0 - 0.8 VDC )

======================================================================
(...)

UCC2720x Application Information

To effect fast switching of power devices and reduce associated switching power losses, a powerful gate driver is employed between the PWM output of controllers and the gates of the power semiconductor devices. Also, gate drivers are indispensable when it is impossible for the PWM controller to directly drive the gates of the switching devices. With the advent of digital power, this situation is often encountered because the PWM signal from the digital controller is often a 3.3-V logic signal which cannot effectively turn on a power switch. Level shifting circuitry is needed to boost the 3.3-V signal to the gate-drive voltage (such as 12 V) to fully turn on the power device and minimize conduction losses. Traditional buffer drive circuits based on NPN and PNP bipolar transistors in totem-pole arrangement, being emitter follower configurations, prove inadequate with digital power because they lack level-shifting capability. Gate drivers effectively combine both the level-shifting and buffer-drive functions. Gate drivers also find other needs such as minimizing the effect of high-frequency switching noise by locating the high-current driver physically close to the power switch, driving gate-drive transformers and controlling floating power-device gates, reducing power dissipation and thermal stress in controllers by moving gate charge power losses from the controller into the driver. (...)

More info about MOSFET gate drivers and high frequency MOSFET switching :

http://www.ti.com/lit/ml/slua618/slua618.pdf

Also search for " TK5Q65W_application_note_en_20180726%20.pdf "

 

[stardustsailor]

DIY IH : Preparing the heating chamber

The Polyamide #6 base ,which will be attached to the bottom of the case .




A VMQ #109 o-ring will insulate the base from the hot cap


Coil attached .


Top panel of case will have a rubber grommet ,that the glass tube will be slightly pressed upon .
A bimetallic disc circuit breaker ( @ 85°C ) will be fitted at the side of the coil .


To be continued .

 

[Diggy Smalls]

Looks cool but way way way beyond my understanding

 

[stardustsailor]

For my first DIY Induction Heater for the VapCap ,I want a portable desktop one !
It's going to be used mainly indoors ,still it has to be portable to be taken along during short trips.

Size is not an issue ,but smaller is better .
It does not have to be water-proof .On the contrary ,rather ...
It has to be reliable and trouble free .

So ,I've started building the device .
I still miss some parts ,still waiting for 'em .

The IH module:
RTV silicone was used to secure the heavy components ( caps & inductors ) to the module.
This is done to protect the -extra thin - copper plane of the pcb from detaching due to vibrations , where heavy components are soldered .

https://electronics.stackexchange.c...or-pcb-mounted-components-to-avoid-vibrations

You can notice the bimetallic disk circuit breaker ( white thing attached to the work coil ) ,
in series connected at the MOSFET switch " trigger " line .
If the working coil reaches at 85 °C ,the NC breaker will open the MOSFET
triggering circuit ( 12 V => 0 V ) and the IH module will be effectively switched OFF ,
until the coil's temperature has dropped well below 85°C,approx at 65 °C .
A simple ,yet very effective " working coil overheat protection ".

https://www.ebay.com/itm/Klixon-The...292215?hash=item4d78549a37:g:kWAAAOSwzrlbV2fj

https://www.yoycart.com/Product/570451079665/

https://www.ebay.com/itm/Thermoscha...hash=item1e91108020:m:mUBmsaBz04AADpGhgrt8ScA

https://www.ebay.com/itm/KSD9700-85...207541&hash=item5b1686a52e:g:jQIAAOSwyP5aSfxv



Some heat-resistant glass fiber cloth is used also,here and there ,as vibration protection also .


The case of the device .Top cover is made of powder-coated steel ,
while the bottom base is made of aluminium .It has lots of cooling air vents.
Made in Greece ,it's price being ~ 5€ .





And the custom-made electromagnetic shield ,inside the case .

 

[stardustsailor]

The working coil is attached to the case with an INOX M4 allen screw .
The IH module will also be attached with High -Temperature double sided tape ,
which I'm still waiting for .

 

[stardustsailor]

Electromagnetic shielding will ensure the trouble free operation of the rest of the electronic components ,
which are operating close to a strong alternating ( at ~ 200 Khz ) magnetic field ,created -mainly -by the working coil .

https://en.wikipedia.org/wiki/Electromagnetic_shielding

http://g3rbj.co.uk/wp-content/uploads/2016/05/Eddy-Currents-final-2.pdf

A thin aluminium plate was used and a piece of thick high quality FR4 pcb ,
with it's copper plane intact .
The shield is a Faraday cage at one of it's sides ,so the working coil can be vented ,
for efficient cooling .

https://en.wikipedia.org/wiki/Faraday_cage









To be continued ...

 

[stardustsailor]

And a short test ...

 

[stardustsailor]

18650 Li-ion cells for IH devices .

Filled with green color all the batteries with capacity > 2000mAh
and with max discharge output current > 15A :



Most commonly high-discharge used cells :

LG : HE2 , HE4 & HG2
Samsung : 30Q , 25R & 25R5
Sony : VTC4 ,VTC5 & VTC6

 

[stardustsailor]

 

[stardustsailor]

The "guts" ...





The exterior ...


When not at zero position ( " OFF " )





The voltmeter switch was placed upside down ,because of it's contacts gettin' in the way ...