What purpose the flash is, might be almost for a cycle lamp. Even if other purposes, it comes into question to be visibly. For pratical use it's better to keep high visibly and to hold down electric power consumption. In principle, that's possible due to make one flash short and keep current strength for one flash.
For an example, case of same current rating and period 0.3 seconds, it's not so different visibly between flash 0.1 seconds and flash 0.05 seconds though, its electric power consumption ratio would be 2 vs 1.
Flash 0.1 seconds with period 0.3 seconds is better visibly and holds down lower consumption than flash 0.2 seconds with period 0.5 seconds.
Admitting that, it has limitation to make flash time short. Maybe around 0.05 seconds is limitation, which depends on the circuit and its program, voltage, current.
Relaxation Oscillator is none other than the discrete circuit which could control such requisites. As a discrete, it would be only one. Of course it's kinda difficult to control, e.g. it comes to be difficult to keep current strength due to flash too short period. However relaxation oscillator is better by far to be made visibly and lower consumption than vibrator and ring circuits. It would be more accurate to say that vibrator and ring circuits are no good for efficiency.
If it needs to control period and flash time, current and so on, it has no choice but to use AVR or PIC, IC programmabled or to divert IC of ready made products.
This page about "tail lamp" introduces various circuits for cycle tail lamp.
There is no difference as a semiconductor, but difference digits of current ratings, between a bombshell LED and a Power LED.
Depends on the shape, a bombshell LED is more likely to be high directivity e.g. angle cut by half around 15 ~ 30 degrees, a Power LED has no directivity which needs collimator or reflector to make directivity.
A Power LED is normally for high current strength, it needs cooling device essencially. Cooling body is all to use a Power LED which remark is found here and there.
Recently there are high current and high illumination bombshell LED which has thick legs for cooling.
A reason of constant current circuit recommended. A reason of cooling body concerned.
Heat over the maximum rating makes LED to bring degradation and failure. Otherwise heat not over the rating though high heat has possibility to bring some problems. Cause high heat makes Vf of the LED lower, it brings overcurrent to the LED with resistance driven under constant voltage. That brings more heat and makes Vf lower as a vicious cycle. As a matter of a bombshell LED with dozen mA current has no problem with resistance under constant voltage.
It's enough to use simplistic constant current circuit with two transistors(right picture, A = Vbe / R) instead of high efficient switching power supply. Any constant current circuit should be used for a Power LED.
By the way, there are many constant current LED driver in market with doubtful circuits. Those are not high efficient and have high heat. It's needed to take pains to make the incidental twelve voltage for use such drivers isn't it.
A rechargeble NiMH battery is desirable to be long life. Most important approach is making no degradation due to over discharge though, it's easy to over discharge due to use for light.
Recently there are much lights with a Li-ion battery. A Li-ion with protection circuit would stop to discharge at proper final voltage, i.e. it would not be used at unexpected timing. It's not that no need protection circuit which has a risk to fire and explode due to over discharge.
It's passable and valid to use a NiMH battery for light in guessing, cause elctric density of a NiMH has come to close to a Li-ion's. Besides for hand-build light such a risk should be fended off in guessing.
As for a NiMH there is almost no risk though, its life come to be very short due to over discharge.
As discharge features of a NiMH, voltage drop is very small, when drop of intensity of illumination could be noticed it might be over discharged. Voltage drop of gadget with dcdc could not noticed especially.
In shortpoint it's concern to know the timing for exchange.
It's best to have a battery indicator. It's better to have a monitor lamp turned on in case of closing to the final voltage. Without such items, if it could be exchanged earlier it doesn't make to over discharge. And case of earlier exchange, it's suggested to use a discharger cause continuation charging makes battery memory effect. A discharger will stop at proper final voltage and help to keep battery good condition.
By the way proper final voltage is certain voltage should be stopped with certain load. Proper voltage might be exchange due to impedance of load.
Please refer to
this page named "discharger" in depth.
