With the PWM system, that is to say, pulse width modulation, it is possible to gradually turn a light bulb 12 V continuous periods of time adjustable from 2 to 25 seconds. Very useful in the car (if you have a little mind "tuning") or at home if you use light bulbs low voltage direct current (solar house) or if you want to further increase the retro aesthetic of your tube amp.
If we connect a generator sawtooth wave and a ramp generator to the inputs of a comparator, we obtain a circuit PWM (Pulse Width Modulation) to turn gradually to a 12 VDC bulb. This arrangement can also be adjusted at will the time it takes for the bulb to go from full brightness to off (adjustable between 2 and 25 seconds).
This circuit can be installed, for example, within an amplifier (one of those we have proposed, why not?) So that the bulb illuminating the VU meter lights up gradually ( in a tube amplifier, it is needed most!). After all audiophiles have also both eyes between the ears. But maybe in your car that you want to mount it: you can then turn on the ceiling or even lights and lanterns in a progressive manner (you'll even have the satisfaction of the vehicle prevent bulbs thermal shock can shorten their life). Again, if you have a car collection, it almost goes without saying ... Sick of "tuning", you get the idea.
Figure 1: This drawing represents the lighting of a lamp at three different times. Its brightness is inversely proportional to the length of time the duty cycle of the signal remains at logic high. In other words, the lamp brightness gradually increases gradually as the high logic level signal shrinks.
The circuit diagram
As soon as power is supplied to the circuit, the current generator IC1 LM334 (see the wiring diagram in Figure 2) C3 maximum load at its terminals and produces a voltage ramp from 0 to 12 V with a variable duration of 2-25 seconds depending on the cursor position of the trimmer R5. When we cut the power, the transistor TR1 into conduction between C3 and discharge so that at the next power cycle begins again with the same period, according to R5.
The operational IC2 / A, contained in the LM358 is used as oscillator for producing sawtooth waves at a frequency of about 1600 Hz is the value measured on our prototype, but yours will perhaps be a few hundred Hz above or below (this will not affect the smooth operation of the assembly). The sawtooth waveform present at the terminals of C4 is sent to the non-inverting input of IC2 3 / B, a voltage comparator consisting of second operational amplifier contained in the LM358. The voltage ramp, channeled through the inverting input 2 of the same comparator, determines the variable duty cycle of PWM square wave signal at the output of IC2 1 / B.
The lamp brightness is inversely proportional to the time the duty cycle of the PWM signal remains at logic high, as shown in Figure 1: wider is the pulse duty cycle, as long as the signal remains at logic high and lower the brightness of the bulb, gradually as the pulse width narrows to logic high, the brightness of the bulb increases until it reaches the maximum value. We used a P MOSFET IRF9540 "tough" it is indeed capable of supporting a load up to 10 A, so we can use a bulb very greedy (over 100 W! Attention to the vehicle battery anyway) .
Moreover, thanks to the PWM, we can connect to our circuit bulbs strong enough (and greedy ...) without the MOSFET does not heat excessively because, working as a switch and not in its linear region, it dissipates minimal power and only for phase power.
It does not stop you but if you plan to use light bulbs consume more amps, mounting the MOSFET on a sink (type ML26) or, as shown in Figure 8, against the wall of the metal housing. But this last point us out the wiring diagram to enter the ground floor in the practical realization.
Figure 2: Diagram of the PWM circuit to turn gradually variable 12 V bulb at a time freely adjustable from 2 to 25 seconds (using the trimmer R5). For a PWM system, we connected to the inputs of the comparator IC2 / B generator sawtooth wave (the operational IC2 / A) and a ramp generator (the integrated circuit IC1 with the capacitor C3).
Figure 3: Pinouts of the integrated circuit LM358 (dual op-amp) seen from above, the MOSFET IRF9540 seen from the front and the BC557 transistor and integrated circuit LM334 (both boxes TO 92) seen from below. 
Figure 4a: Layout diagram of the components of the plate for the progressive lighting lamp 12 V. The P-channel MOSFET that we chose has a load up to 10 A. For proper mounting, the metal plate should "look" R1-R2. 
Figure 4b-1: Drawing to a wide, double-sided PCB with plated through holes of the plate for the progressive lighting lamp 12 V EN1648 side seams. 
Figure 4b-2: Drawing to a wide, double-sided PCB with plated through holes of the plate for the progressive lighting lamp 12 V EN1648-side components. 
Component List
R1 ........ 47
R2 ........ 10 k
R3 ........ 10 k
R4 ........ 1 k
R5 ........ 10 k trimmer
R6 ........ 100
R7 ........ 10 k
R8 ........ 10 k
R9 ........ 100 k
R10 ....... 47 k
R11 ....... 10 k
R12 ....... 100 k
R13 ....... 47
C1 ........ 100 uF electrolytic
C2 ........ 10 uF electrolytic
C3 ........ 10 uF electrolytic
C4 ........ 3.3 nF polyester
C5 ........ 100 nF polyester
DS1 ....... 1N4150
DS2 ....... 1N4150
TR1 ....... PNP BC557
MFT1 ...... IRF9540 MOSFET P
IC1 ....... LM334
IC2 ....... LM358
Note: the resistors are 1 / 4 W.
The practical realization
This arrangement is within the reach of a beginner.
To build this small (but powerful) device, you need the double-sided printed circuit with metallized holes EN1648, on which all components are mounted, except perhaps the power MOSFET (see Figure 8) that can be set against a wall of the metal box, inside: 4b-1 and 2 shows drawings of the two sides across one. Make it or get it.
When you have before you, get first the support of IC2 and check out this first work (or short-circuit between tracks or pads or cold weld joints) and then climb all the other components from the lowest (resistors , diodes) to the highest (trimmer, capacitor, transistor and LM334 in boxes TO 92, MOSFET-see Figures 7 and 8 - and terminals).
Check before welding the orientation of the polarized components (electrolytic diodes-rings to and from C5-R7, transistor and LM334-flats to the left-and the integrated circuit, inserts it into the socket after installation in the case and the last connection made).
No problem if you look closely 4a to 8 and the list of components.
Be sure to check several times, identification and orientation of components and quality of all welds, then go to installation in the housing.
The installation in the housing
Of course, this arrangement in a metal enclosure is optional: if you use it, as we have suggested, for the progressive lighting of the backlight of the VU meters on your amplifier, you will go directly into the small platinum it.
If this is not the case, take the small aluminum case (see Figures 6 and 8) and drill four holes in the bottom by using the platinum (already drilled) as a drilling template, in the process, drill two holes about 10 mm in the two major opposing sides.
In the four-hole mount four metal spacers 5 mm in both holes insert two rubber-pass son, set the plate on the spacers with four screws and do enter / exit the son of two 12 VDC power supply and two son going to fly to the bulb. Use the wire diameter is commensurate with the current consumed by the load (do not skimp on the diameter).
If you chose the option "setting the MOSFET against the inside" or if you Give it a MOSFET heatsink, do not forget to interpose between the metal plate and the metal of a sink support insulation kit composed of an insulating sleeve for the bolt and a mica surface for the sole.
All connections are made and verified, you can insert the chip into the socket with great care and common sense-reference keyed-U to C5. If you are a beginner, take right away this excellent habit.
Figure 6: Photograph of a prototype of the plate for the progressive lighting lamp 12 V EN1648 MOX30 installed in its case (you will need to drill to attach the plate to the bottom with four spacers, to let the son of two 12 V power supply and to let out the two son going to the load). 
Figure 7: To ensure the MOSFET heat dissipation MFT1 high, mount it directly on the metal housing (Figure 8), without forgetting to use the insulation kit (grommet and mica). 
Figure 8: Before inserting the plate into the metal casing, drill four holes in the bottom of it (using the plate as a drilling template) and tighten four metal spacers of 5 mm (the slight elevation of the plate from the bottom the metal case will prevent short circuits). Drill two holes for the son of input and output voltage in the two long sides and place the rubber-pass son. Attach the legs of the SDG MOSFET points of the plate with the son of different colors so as not to invert (see Figure 7).
Figure 9: tension12 V to power this circuit is applied to the terminal and left the lamp to the right.
Figure 10: If you withdraw the voltage 12 V vehicle battery, the son of the negative input as the output can be connected to the chassis (ground) of it.
Setting
With a small screwdriver adjust the slider to half way the trimmer: for example, upon powering up the circuit you can check the ignition phase of the bulb.
This is of course a 12 V and you feed DC (eg vehicle battery or power supply of the amplifier: in the latter case, if necessary, mount a controller 7812). See Figure 9.
Turn: the brightness of the bulb gradually increases at a rate depending on the setting of the trimmer. To set the duration (how long it takes the bulb to reach its maximum brightness), you will proceed by trial and error each time by acting on the trimmer, but still proceed to set off device.
Turn the screw on the trimmer and then feed the machine and see if this setting for you, otherwise turn off the power and touch up the trim in one direction or the other and then turn the power on, etc..
If you are considering a used car to a gradual lighting fixtures, even as the lights and why not the lights, see Figure 10: Mass for the son (both input and output), be sure to link them to the body, but made good ground connection (the metal must be free of paint and rust). If you apply gradual ignition circuit of the headlights of the car, get two circuits (with one you could melt the MOSFET) and set the duration to a minimum.
If you are not keen, get help from a friendly mechanic (yes it exists!) Or by an electrical car: it will save you perhaps disappointments (in the vehicle, it is most dangerous, just after the driver, the fuel tank and the electrical circuit).
The information is vary useful. thank you for sharing.
ReplyDeleteWire Harness Manufacturer in India | Wire Assembly Manufacturers in India