I hope I do not sound stupid. I am good at soldering kits together but do not understand all what is going on with the electronics. I have a 5 led random/sequencer flasher kit I purchased and built. It works good but I want to slow the flash rate down quite a bit. I know the trimpot controls the speed so is it as simple as putting in a different trimpot? If so, how do I figure out which one? The schematic of the kit can be found at
The kit doesn't identify the integrated circuit that contains the oscillator and controls the LEDs.
It is probably some kind of CMOS chip - the Vss label on the circuit diagram suggets as much - but you are going to have to take a close look at the chip to see if you can see some kind of part number on it before we could be all that much help.
The situation doesn't look promising. If there was an explicit capacitor on the schematic, it would be easy enough to replace it with a higher-capacitance part which should then give a lower the oscillator frequency. The absence of an explicit external capacitor suugests that the circuit might rely on an internal capacitor, possibly part of the integrated circuit, which you wouldn't be able to get at.
A higher value potentiometer might lower the operating frequency, but all the potnetiomenter ranges I know stop at 1M so this isn't a practicable option.
This kit seems to use a GT-2391 "chip on board" module, and a quick search does not find a datasheet. But there's a good chance that you can indeed slow it down by changing the trimpot. It currently seems to be 600k; it's quite likely that doubling the value will halve the speed, assuming that it currently gets slower as you move the pot towards the higher-resistance end. How slow do you want it to be? There will eventually be some sort of limit. Curiously, the circuit doesn't seem to have any capacitors in it...
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That seems highly unlikely in that the first sentence in the link:
"This cmos VLSI single chip-on-board is designed for
electronic toy and warning light applications."
identifies "chip-on-board" (COB) as the means used to affix the chip
to the board.
In that method of construction the bare die is affixed to the traces
on the PCB and then covered over with a dollop of epoxy in order to
protect it mechanically and environmentally.
Consequently, there is usually no way to identify the chip or its
internal circuitry.
Not exactly true. There are solvents designed to soften epoxy resin, and once you've got rid of the blob of epoxy, you can look at the surface of the chip where there is usually some kind of mnufacturers logo and a part number.
Back when I did this, a good optical microscope could give you enough magnification to read the logo and the number. You might need an electron microscope these days.
The OP probably hasn't got access to this sort of gear, so you aren't really misleading him.
True,
..
I couldn't find any in the Farnell catalogue, so I don't think "common as dirt" is entirely accurate. And dirt is a problem at that sort of impedance - if you aren't careful about washing off residual flux, you don't exactly see 5M between the pins of the device.
It does look as if the pot is being used as a rheostat, but that is an assumption.
Another assumption.
Getting resistors over 1M is not entirely trivial - they are readily available, but do have to dig through the catalogues to find them.
It isn't altogether clear that the Osc1 or Osc2 inputs to the chip would respond well to an external clock. Some chips certainly can be driven in this way while others might be less happy - in many applications one of these two pins is a logic output, and driving a logic output can overload the drive transistor inside the chip.
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Hmmm...
As usual, you seem to have taken information which was provided you
after the fact in order to pretend that you knew what was going on
before the fact.
Sorry to have to correct your spelling John... it's "Slowman" ;-)
...Jim Thompson
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| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
Like you say, I don't get around much these days, and I've not run into "chip-on-board" (COB) construction in hobby stuff before. In the good old days, back when Jim Thompson hadn't lost his marbles, you generally could work out what a hobby chip was by looking at the package =2E
..
1...
No, just painful experience.
If you believe the schematic ...
Well, I spent enough of my life being a winner not to be too worried about this. At least I didn't lose big time, and end up stuck in rural Texas.
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Damn, but you\'re an overbearing ass and, as usual, you\'re so damned
stupid you can\'t even figure out the meaning of what was being
written.
Here: let me see if I can get through to that fetid pile of
decomposing offal you call your brain...
First, note that when one writes: "blob of epoxy", the quotes are
supposed to indicate that the text contained between them is an
exact, bona fide copy of what someone else wrote.
Next, note that you incorrectly attributed that text to me since
what I wrote was "dollop of epoxy", not "blob of epoxy".
Finally, I can find no reference to a dollop changing into a blob as
a result of some arbitrary process, so your claim that it does is
inaccurate.
As a matter of fact, my Webster\'s defines dollop (the noun) as:
"1. a lump or blob of some substance. 2. a small amount: a dollop
of whipped cream."
So, your: "Once the dollop has set, it ceases to be a dollop."
is wrong, since both words have the same meaning.
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
Jim does have delusions of sophistication. The redneck from West Virginia has pretty much cornered the local market in ignorance, but thinks that people who don't share his numerous misconceptions are ignorant - where a better label would be well-informed.
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