Hi,But now that I think about it , I guess I can use the 4017 IC and simply take the P mosfets and couple two mosfets for each 4017 output.
The mosfets will be low voltage low current ones so very little gate charge, I hope the 4017 10mA output per pin should be enough to drive two fets simultaneously?
Then I could add a little delay in how fast the gate discharges and that should give me about 4 to 6 switches OFF at any given time as the position travels along.
Well I used the "LED chaser" as a reference in order to make myself clearer to folks.There are many ways to make a LED Chaser with any pattern , direction and rate of change at reasonable speed but what's the big deal about "1000 km/h".
That is not going to be possible.
Consider 5mm LED with 5mm spacing to find out the pulse time for a distance, d, (1000 km = 1e9 mm) and velocity, v.
t= d/v = 5 mm / 1000 kph = pulse time for 1 LED => 5 mm / 1e9 mm / 3600 s = 1.4 ps ( that's pico seconds about a million times to fast)
Using 25 ohm drivers with 3.6V logic @ Vdd < 2V, you do not need resistors but you do need to mind the power dissipation.
View attachment 179407
I won't give you a serious practical circuit until you give better design expectations "SPECS"
Why do you need this, what brightness, which LEDs, power, current , budget?
By inverting the LEDs you can invert the function of a Johnson Counter, but 74HV17 CMOS is high voltage and also high resistance meaning low current, so that won't work well. I made a ficticious 16 stage Johnson Counter.
Hi,
1000 km/h = 1000/3600 km/s = 0.278 km/s or 278m/s = 277,777 mm/s
v = s / t
or
t = s / v = 5mm / 277,777mm/s = 18us
Klaus
Let's say a two parallel opposite direction diodes where the one letting current back from gate has a larger resistor in series?
OOPs I forgot the brackets d=5 mm / v= (1e9 mm / 3600 s) = 18 us per 5mm which is one half of 55.55... kHz or about 1k faster than your eye can detect clearly.t= d/v = 5 mm / 1000 kph = pulse time for 1 LED => = 1.4 ps ( that's pico seconds
CD4017 drive currents :Hi,
From memory, 4017 is not a 10mA sinking or sourcing device, by a long shot, sorry. Except for a low-power input, more poweful output, switch of some kind between a 4017 and the MOSFETs, or using 4017 + modern BJTs that have comparably low RDS(on) to MOSFETs to drive your inputs, no suitable part comes to mind right now.
For what you described about fast on&slowfade off, I'd possibly use a diode + current-limiting resistor in the MOSFET gate turn-on path and an RC network in the turn-off path (or vice versa, depending on what you end up using).
Ok, I've built this device, not like the one in the video but different, it works, if you or anyone else is still interested in why I've built it I will make a new thread explaining my experiment you could come and comment there if you wish to, thanks for your participation so farOOPs I forgot the brackets d=5 mm / v= (1e9 mm / 3600 s) = 18 us per 5mm which is one half of 55.55... kHz or about 1k faster than your eye can detect clearly.
I still have no idea what you want to do from your descriptions.
Try harder.
"just need a row of switches that switch few milivolts " ....
"Since these switches will be mounted on a rotor.
It (1000 kph) is nothing more than angular velocity."
I suspect you are talking about a POV display oops I mean a POV LED display.
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