what if we change the 1uf cap to .1 uf? it would discharge quickeraudioguru said:Hi Max,
Clarification:
1) Of course the ICs have resistors inside. The LM3914 has a bunch of resistors between pins 4 and 6 that determine what input voltage lights its LEDs, and the 555 has resistors that determine the lowest and highest voltages of its timing cap.
2) Of course the circuit has changed from my original one, now the 1uF cap is the 555's timing cap, which never discharges to ground like it did in my circuit.
3) Inside the LM3914 between pins 4 and 6 are 10 resistors in series, that are used as a voltage divider. This voltage divider determines what input voltage turns on the LEDs. Now that the 1uF cap is used as the 555's timing cap, the cap's voltage will range from 1/3 of the supply voltage for its discharged voltage, to 2/3 of the supply voltage for its highest voltage. The 555's 1/3 and 2/3 of the supply voltage reference points are determined by a voltage divider of 3 resistors inside the 555 that are connected between the supply and ground.
4) We must duplicate the 555's voltage divider with another voltage divider for the LM3914 so that the 1st LED lights when the cap's voltage (input to the LM3914) is 1/3 of the supply voltage (the cap is discharged by the 555) and the 6th LED lights when the cap's voltage is a little less than 2/3 of the supply voltage (cap is at its highest voltage). It would be a lot easier to calculate voltages if the 555's cap voltage simply ranged from ground to a fixed voltage. It would also be a lot easier if you had 10 LEDs instead of only 6.
5) The 1st scan is longer because the cap must charge from zero volts (fully discharged from the circuit being unpowered) to 1/3 of the supply voltage before the timing actually begins. The LEDs will be off during that time.
6) You must measure the LM3914's voltage divider total resistance between pins 4 and 6 because the datasheet says that it could be anywhere from 8K to 17K ohms. We must know exactly what it is.
IC's are lousy at making accurate value resistors, but can make very accurate duplicates and ratios that are used in "normal" LM3914 and 555 circuits.
BTW, the emitter of the 2N3906 current source and its resistors must now connect to the supply voltage, instead of to the LM3914's pin 7. Pin 6 must also be disconnected from pin 7. Pin 4 must be disconnected from ground.
internal delay of IC555 that will discharge cap much less then 1/3 Since the cap is now shorten threw pin 5 of ic555... If you think this schematic looks allright and no other modifications are needed please identify tha values of all resistors, my specs for LED's are posted above.... at least 20mA per Led would be goodaudioguru said:Hi Max,
Sure 0.1uF would discharge quicker. 0.01uF or 0.001uF would be even quicker! 100 puffs (slang for picoFarads)? or just 10 puffs?
In order for the timer's period to be about 1 second per scan, the capacitor's charging current must be low. The time calculation is roughly one divided by the current, times the capacitor's value. So if you reduce the value of the capacitor then the charging current must also be reduced by the same amount.
The problem with having a very low charging current is that pins 2 and 6 of the 555 need a small current to operate, and may steal all of the very low charging current, leaving the capacitor with nothing. Actually, the currents for pins 2 and 6 are opposing, so that the current required by pin 6 can be supplied by the current from pin 2. The datasheet spec's a current for pin 2 but not for pin 6, so maybe they are not equal.
Since the current for pin 2 is spec'd with a wide range, I wouldn't risk operating the 555 with a very low charging current and would stay with using a 1uF (low-leakage metalized poly) cap.
well if using ref voltage of LM3914 v have to lower voltage of 555 too.audioguru said:Hi Max,
Are you saying that the 1uF cap will be discharged so quickly that its voltage will overshoot the 1/3 of the supply voltage that triggers pin 2, because the internal delay of the 555 will release the discharge transistor at pin 7 too late?
It could be, but I don't think the capacitor's discharge voltage will overshoot much. If it does, the voltage level for the 1st LED to light can be adjusted to be the same voltage.
Why do you have a resistor to ground at pin 5 of the 555?
It would just lower the capacitor's maximum charge voltage directly, and lower the cap's minimum voltage half as much.
Allright I came up with this finally and ordered the stuff i need. But i still want to try out with a voltage limiter. Also I looked at my bikes wiring when the switch is on for right or left turn signal it runs threw a turn signal relay and then to the bulbs and the indicator lights. will that relay effect this?audioguru said:Hi Max,
Sorry for my delay.
I don't like the way your new diode pulls down the 555's pin 5 so low that the flip-flop inside the 555 may "latch" and not be able to be triggered by pin 2.
To avoid the problem of a delay on the 1st cycle of the 555, I have been thinking to leave the 555 and the current source transistor powered whenever the bike is running, with pins 2 + 6 and the cap held at a voltage just a little lower than pin2's threshold voltage. When you activate a turn signal switch, the LM3914 will be powered and immediately indicate the 1st LED. At the same time, the voltage limiter on the cap will be released and it ramps normally along with the other LEDs.
I will sketch a "voltage limiter" and the resistors for the current source soon.
damn i wish i would of looked at my bikes wiring schematic earlier because that would of saved me some time and money. well we can try it that way.audioguru said:Hi Max,
This project is becoming a can of worms.
The 2.2K resistor that you put across the cap steals current from the current source so the cap will no longer charge linearly, and may not even charge high enough to allow the 555 to work.
You mentioned a relay. I didn't know bikes use an expensive and failure-prone relay flasher when an inexpensive, simple electronic circuit can flash reliably. In a car, its clicking reminds you to turn it off, but on a motorcycle can you hear it?
Why use this complicated 555 circuit when the flasher can do it very well?
The flasher can apply power to the current source transistor which linearly charges the cap. The LM3914 is also powered and indicates the rising cap voltage on the LEDs. When the flasher clicks off, the LEDs also turn off and a P-channel junction FET quickly discharges the cap. When the flasher applies power, the FET is turned off.
Really simple, do you like it?
I don't think it flashes "faster" when one is burnt out but it does flash faster when you change out the stock bulbs (they were never LED's) some people say that when they added LED's to just Flash they would flash faster then stock bulbs did. Also i think if one rea bulb is broken then other rear one doesn't work. i will reconfirm this tommaro i have to get to bed but i think either way fast or not as long as the Bar mode comes on where people can see its a faste bar mode not just a flash it should be good to go. so lets just try that with the new FET control. and i will give you specs of how bulbs work on the bike for sure tommaroaudioguru said:Hi Max,
One thing about the flasher relay on cars: the flash rate becomes very fast when a light bulb is burnt out. So it might be fast on your bike when using low-current LEDs instead of a high-current light bulb. If you use the LM3914 in its Bar mode, the rate might start fast then slow during each scan.
For cars, a "heavy-duty electronic" flasher was available to drive additional lights on trailers, etc. Their rate doesn't change with load changes. Maybe they are still available and will fit your bike.
If your bike had 12V light bulbs, this circuit (the current source transistor circuit, the LM3914 and the new FET control) connects to their wiring. If it had LEDs, you must connect before their current-limiting resistor.
Allright this is what my friend told me he owns the same bike, he has LED's in pegs but they only flash no sequencing (barmode)Maxer said:I don't think it flashes "faster" when one is burnt out but it does flash faster when you change out the stock bulbs (they were never LED's) some people say that when they added LED's to just Flash they would flash faster then stock bulbs did. Also i think if one rea bulb is broken then other rear one doesn't work. i will reconfirm this tommaro i have to get to bed but i think either way fast or not as long as the Bar mode comes on where people can see its a faste bar mode not just a flash it should be good to go. so lets just try that with the new FET control. and i will give you specs of how bulbs work on the bike for sure tommaroaudioguru said:Hi Max,
One thing about the flasher relay on cars: the flash rate becomes very fast when a light bulb is burnt out. So it might be fast on your bike when using low-current LEDs instead of a high-current light bulb. If you use the LM3914 in its Bar mode, the rate might start fast then slow during each scan.
For cars, a "heavy-duty electronic" flasher was available to drive additional lights on trailers, etc. Their rate doesn't change with load changes. Maybe they are still available and will fit your bike.
If your bike had 12V light bulbs, this circuit (the current source transistor circuit, the LM3914 and the new FET control) connects to their wiring. If it had LEDs, you must connect before their current-limiting resistor.
thanks
Max
Hey mango_Grailmagno_grail said:Maxer,
If I had a better idea of what you were trying to do I could have given more useful information. Various make bikes use different methods for flashing the signals. Usually the older bikes use a thermal relay like the antique cars. Current passing through heats a bi-metalic strip which opens the circuit, then cools off and closes again. Low wattage bulbs or one burned out will cause the other bulb to light but not flash (not enough current). That is why LED bulbs do not work in these bikes. Others, like my '97 Triumph use the ECU to flash the bulbs using a relay to carry the current. No change if a bulb burns out or replaced with LEDs.
Older bikes use the opposite signal bulbs to provide the ground path for the dash indicator.
Pre-80's British bikes are positive ground. Everything else, I believe, is negative.
Another point, most high ouput LEDs have a low visibility angle, some as little as 20 degrees. Someone in the next lane might not see your signal if they are too close (disregarding the fact that will not see it anyway as they are too stupid).
audioguru said:Hi Max,
This project is becoming a can of worms.
The 2.2K resistor that you put across the cap steals current from the current source so the cap will no longer charge linearly, and may not even charge high enough to allow the 555 to work.
You mentioned a relay. I didn't know bikes use an expensive and failure-prone relay flasher when an inexpensive, simple electronic circuit can flash reliably. In a car, its clicking reminds you to turn it off, but on a motorcycle can you hear it?
Why use this complicated 555 circuit when the flasher can do it very well?
The flasher can apply power to the current source transistor which linearly charges the cap. The LM3914 is also powered and indicates the rising cap voltage on the LEDs. When the flasher clicks off, the LEDs also turn off and a P-channel junction FET quickly discharges the cap. When the flasher applies power, the FET is turned off.
Really simple, do you like it?
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