Help with DT Project (includes an inductive charger).

Thread Starter

Engineer wannabe

Joined Jan 13, 2020
9
Hi Everyone,

my DT project includes an inductive charger. I would like to build a circuit that when a voltage is received from the inductive charger (9Vdc in ~5Vdc out) one LED blinks then after 10s it remains constant. Then turns off when voltage is stopped.
I’m not entirely sure how to go about designing and making this circuit, any help would be much appreciated!
Thank you :)
 

ci139

Joined Jul 11, 2016
1,088
Option 1 : if your "5V" has the voltage you can directly power the led at the receiver side making it blink or not / if your "5V" has no power - the LED is off

Option 2 : keep the LED at transmitter side & determine the presence of "remote load" by increased current through the transmitter (this may be difficult to implement if the REMOTE LOAD does not consume significant power)

LED behaviour : has many implementations ranging from the analog to the digital to the micro controller based


• the micro based - requires probably one additional mos-fet if you want intense LED light

• the principial analog control can be achieved by using random squarewave oscillator and 10s interval timing to fix it at ON state after that period
↑ this requires 3 transistors

• the digital implementation can easily be achieved by CD4060 (a bit less complex v. than in the video)
 

ci139

Joined Jul 11, 2016
1,088
since i don't know what you know (about misc. eletronics) , also what kind of inductive charger you got , also your system overall setup ...
... i provided a minimal guidance

also i've been only slightly glanced on inductive transfer circuits coz there's been no need to use one - i am however able to boost educate myself on this matter (in minutes) while required

so, ask, if there's anything else to get started
 

Thread Starter

Engineer wannabe

Joined Jan 13, 2020
9
since i don't know what you know (about misc. eletronics) , also what kind of inductive charger you got , also your system overall setup ...
... i provided a minimal guidance

also i've been only slightly glanced on inductive transfer circuits coz there's been no need to use one - i am however able to boost educate myself on this matter (in minutes) while required

so, ask, if there's anything else to get started
Thanks I think I might just use a very simple circuit with transistors and resistors that I found online. I only have a very basic knowledge about electronics :)
 

ci139

Joined Jul 11, 2016
1,088
(i can't make simple circuits) basically the circuit in #14 is suitable for generating the 10s delay
however when it's modified it can and oscillate /!\ but it will be very sensitive to supply voltage and noise /!\ -- not very reliable nor practical
Startup~Osc_v3.png
_____________
the CD4060 does the job a bit better (while micro' takes the least components and space)
LED goes to PNP or p-MOS-Fet amplifier at p7 "T0" (so it's ON when the p7 is Low)

+ there should be 1N4148 in series with 4k7 resistor from Vdd to GND that allows the capacitors to discharge
also a reverse 1N4148 in parallel with R8 (as the D4 is to R3) -- helpng the C4 discharge faster

incase te circuit wont start the R3 C2 and R8 C4 must be replaced with the bigger ones

the circuit is not designed to respond on quick swapping the energy receiver next-and-away from transmitter
for this↑ - it takes additional circuitry -- the capacitor from Vdd to GND + voltage detector that triggers , say , below 4V Vdd and shorts C3 and C4 to the ground (every next handle pushes your design more complex -- this is why using an MCU instead could pay off . . . or . . . simple 555 timer . . . with the LED )

CD4060 - 10s - delay - Timer.gif
 
Last edited:

crutschow

Joined Mar 14, 2008
24,125
Below is the LTspice simulation of a 555 astable circuit with delayed off:
Due to the tolerance of M1's turn on threshold, you may have to adjust the value of R4 to get the desired 10 second off delay.
The LED pulse period is ≈1 second with ≈200ms pulse.
R1 + R2 determines the LED Off time and R2 determines the On time.

1579280317298.png
 
Last edited:

ci139

Joined Jul 11, 2016
1,088
the 555 and the MCU and Op-Amp/Comparator solutions have the advantage that ← these things usually have a wide supply range and allow the supply voltage independent designs
_______________

when the 1.5V battery is full it may have (depending on type/chemistry) the terminal voltage up to 1.8V as it looses charge the terminal voltage drifts down to 0.9V (voltage ratio/-change up to 2:1) . . . for the lead acid car or UPS battery the full/empty voltages have 4 to 3 ratio e.g. 12V full - 9V empty

the most designs become difficult from the above fact +

if it's mains transformer - then (due to it's internal resistance) , when the load is becoming heavier - it drags down the initial rectified voltage , say 24V even below 6V (input voltage change 4:1) ← such introduces a NEW problem : diffused power . . . that's why we have SMPS nowadays (enables more compact and literally more Cool design)

in your case it (the input voltage range/drift) likely isn't that big issue -- but it can't be overlooked

the transistor designs can also be tuned to work in specified supply range - but the 555 and the MCU and Op-Amp/Comparator and appropriate supply range CMOS logic families make it all more easy to achieve
 

ci139

Joined Jul 11, 2016
1,088
i managed to make the BjT version a bit more robust . . . but it still is very sensitive to the Vs
but it's always possible to put the timing chain under regulated voltage . . . the BjT circuits work down to 680mV and even 420mV Vs , they work much better (faster) above 1.26V Vs , even more better above 1.53V and a lot of better above 1.66V -- the simple discrete Op Amp and it's common mode (also bipolar SCS Latches) start working above 1.86V (BE drop 650mV + complementary CE drop 380mV ... leaves some 830mV (45%) on biasing resistors) and start working better above 2.16V Vs (BE drop 650mV + complementary CE drop 380mV ... leaves some 1.13V (52%) on biasing resistors) ← so using the simple TL431 (1.6 ... 2.8 V) shunting regulator is a fastest good option . . .
__________
▼ the functionality (similar to the figure below) can also be achieved by using a basic two transistor Flip Flop + 1 more DTL based ...
? AND OR NAND NOR ? -- depending on polarity and optimum configuration ... LED-amp (Fig.3) -- where 1 input serves as 10s timer
e.g. -- a similar to the below but with 3 transistors
LED - Flasher -- TEST -- xa1.png
__________________________
so much about the 3 transistor v. (← it can be done . . . perhaps done better with the MosFET timer -- but will not be too practical)
LED - Flasher -- TEST -- xa3.png
 
Last edited:
Top