audioguru2
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Use bigger battery cells, C or D cells instead of little AA cells.steev said:
audioguru2
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The MAX660 is a high current voltage doubler.
With a brand new 3V battery powering three 3.6V white LEDs through the three 1N4148 diodes, the light will be extremely bright and the battery's current will be very high for a few minutes if the LEDs don't fail due to over-current. Then the brightness will decrease as the battery voltage runs down since the MAX660 doesn't have a voltage regulator.
The circuit doesn't save any current. The battery won't last long.
With a brand new 3V battery powering three 3.6V white LEDs through the three 1N4148 diodes, the light will be extremely bright and the battery's current will be very high for a few minutes if the LEDs don't fail due to over-current. Then the brightness will decrease as the battery voltage runs down since the MAX660 doesn't have a voltage regulator.
The circuit doesn't save any current. The battery won't last long.
audioguru2
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Why do you need 6 LEDs?
A single ultra-bright white, blue or green LED will shine down the street or across the street at night.
If you reduce the current then the battery will last a long time but the light won't be bright.
You can use a Cmos gate IC to make a fast oscillator to blink an LED and a slow oscillator to make a long pause in the blinking. The Cmos gates can drive a transistor to give plenty of current to the LED for it to be bright, and since it doesn't draw current when it is between blinks then the battery lasts a long time.
A single ultra-bright white, blue or green LED will shine down the street or across the street at night.
If you reduce the current then the battery will last a long time but the light won't be bright.
You can use a Cmos gate IC to make a fast oscillator to blink an LED and a slow oscillator to make a long pause in the blinking. The Cmos gates can drive a transistor to give plenty of current to the LED for it to be bright, and since it doesn't draw current when it is between blinks then the battery lasts a long time.
hi again
we can't use more voltage here as the receiver is rated at 3.6v only.so we decided to go with parallel connection(we found a good high current battery pack).so can u show me a circuit which can flash 5(we decreased the number) LED's with appx. 0.5sec timing gap.
and one more thing is size of circuit.we almost ran out of space.so pls show us some small circuit.
we can't use more voltage here as the receiver is rated at 3.6v only.so we decided to go with parallel connection(we found a good high current battery pack).so can u show me a circuit which can flash 5(we decreased the number) LED's with appx. 0.5sec timing gap.
and one more thing is size of circuit.we almost ran out of space.so pls show us some small circuit.
audioguru2
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You shouldn't connect LEDs in parallel. Their forward voltages will be slightly different causing the one with the lowest voltage to hog all the current and maybe burn out. Each LED should have its own current-limiting resistor.
In my 3V Ultra-bright LED Chaser project I use a Schmitt trigger oscillator from a 74HC14 to drive a transistor to blink its LEDs. You could make a small Schmitt trigger oscillator from a couple of transistors.
View attachment 38625
In my 3V Ultra-bright LED Chaser project I use a Schmitt trigger oscillator from a 74HC14 to drive a transistor to blink its LEDs. You could make a small Schmitt trigger oscillator from a couple of transistors.
View attachment 38625
OOps i forgot.
we r using 5 100Ohms resistors for each(5) LED seperately.to provide exact amount of current.but the problem is with the output supply of receiver circuit.its only working when we feed 3.6volts exactly.and when we connect led to this voltage they r burning out.(i fried up 10 led till now) :'(
i know using lm317 we can get exactly 3volts(thanks to audio guru and ante).but problme is with heat.
in other thread someone said that we can drop voltage by 0.6v using a diode.can i keep voltage exactly 3v from this diode method.or is there any seperate ckt for this (i need circuit as small as possible with no heat generation.)
we r using 5 100Ohms resistors for each(5) LED seperately.to provide exact amount of current.but the problem is with the output supply of receiver circuit.its only working when we feed 3.6volts exactly.and when we connect led to this voltage they r burning out.(i fried up 10 led till now) :'(
i know using lm317 we can get exactly 3volts(thanks to audio guru and ante).but problme is with heat.
in other thread someone said that we can drop voltage by 0.6v using a diode.can i keep voltage exactly 3v from this diode method.or is there any seperate ckt for this (i need circuit as small as possible with no heat generation.)
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audioguru2
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Please attach a schematic of your circuit. I don't understand how your LEDs can burn-out.
A red LED has a forward voltage drop of about 1.8V. Most LEDs have a max current rating of 30mA.
If you have a 100 ohm current-limiting resistor in series with it then 4.5V across the combination results in a current of 27mA. With only 3.6V across the combination of the 1.8V red LED and its series 100 ohm current-limiting resistor then the current is only 18mA. With 3V across the combination then the current is only 12mA.
Anything that has continuous current in it and a voltage across it generates heat. Reduce the heat by reducing the current, extra voltage or both. Your choice of a 12V battery to power the low-voltage circuits wastes a lot of power.
A red LED has a forward voltage drop of about 1.8V. Most LEDs have a max current rating of 30mA.
If you have a 100 ohm current-limiting resistor in series with it then 4.5V across the combination results in a current of 27mA. With only 3.6V across the combination of the 1.8V red LED and its series 100 ohm current-limiting resistor then the current is only 18mA. With 3V across the combination then the current is only 12mA.
Anything that has continuous current in it and a voltage across it generates heat. Reduce the heat by reducing the current, extra voltage or both. Your choice of a 12V battery to power the low-voltage circuits wastes a lot of power.
ohh right.then i miscalculated the resistor value.
problem here is i dono the forward voltage of the led iam using.
i got them from a local electronics shop(shop guy said that he dono LED details).they r bright enough when i connect 2 AA cells in series.
so can i consider its forward voltage as 1.8v.or there any specific method to measure the LED forward voltage
problem here is i dono the forward voltage of the led iam using.
i got them from a local electronics shop(shop guy said that he dono LED details).they r bright enough when i connect 2 AA cells in series.
so can i consider its forward voltage as 1.8v.or there any specific method to measure the LED forward voltage
audioguru2
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If your LED has a forward voltage drop of 1.8V and you connect it to two AA cells in series (3V) without a current-limiting resistor then the extra 1.2V would create a current that is so high that the LED would instantly burn-out!steev said:
You don't say the color of the LED that determines its voltage. My red LEDs are 1.8V, my blue LEDs are 3.1V and my white LEDs are 3.5V.
You don't show a schematic nor say the voltage that is burning your LEDs when they each have a 100 ohm current-limiting resistor. Therefore maybe there is enough voltage to connect some LEDs in series.
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