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| james_s:
--- Quote from: floobydust on August 17, 2019, 04:06:24 am ---This construction barrier flashers I've seen were the incandescent light bulb with a bi-metallic blinky switch inside and a 6V lantern battery. Newer ones are LED and not as bright. --- End quote --- I've never seen one with a bimetallic self flashing bulb, maybe the really old ones worked that way but all the old ones I've seen used a little circuit with 2 transistors to do the flashing, they also had a CdS cell to switch them off during the day. Here are two such circuits I found from someone who reverse engineered a few of these lights. These are tested working circuits from commercial products so if one wanted to build such a flasher one of these is probably a good starting point. |
| floobydust:
It's mostly about a beginner's circuit that mysteriously stops working due to a turn of the potentiometer. That kind of thing annoys me because when you are learning electronics, you already have enough things that can go wrong. It's not easy sometimes. The circuit operation is not explained anywhere, it's just handed to you and when it doesn't work, it can frustrate an experimenter. In those two construction barrier circuits, the tantalum capacitor sees reverse-voltage pulses, and steady reverse voltage during daylight, around -500mV. I was thinking the tantalum cap would fail. But it looks like that is possibly OK AVX tech pdf for up to 3-10% of rated voltage, maybe a volt, but failure rates are not known. I found these flashing light bulbs realizing most people have never seen them before. Some so old they are made in USA and Holland. Trying the KonMari method from Marie Kondo to clean up my electronics parts bins, I think they are only good for artistic value, like a toy robot nose or something. |
| soldar:
--- Quote from: Zero999 on August 17, 2019, 07:04:52 pm ---I find high contrast much easier much easier to read, than fuzzy greyscale. --- End quote --- I agree. Please show some consideration to your fellow forum users and use the least bandwidth possible. My recommendations: Use .jpg only for photos and use .png for line drawings. Post the smallest photo, in pixels and in file size, that shows what you want us to see. Do not post a 5 Mbyte file when a 50 KByte file will do just the same. Some of us have limited bandwidth. Learn to edit, process and compress. Line drawings can be made very clear and very small in file size. I am attaching one just as an example. 6KB. No need to use 60 KB or 600 KB or 6 MB. |
| tooki:
Yes, but it has to be done well. The lower the resolution, the more critical the preparation becomes, and frankly, for scanned things, it needs to be quite detailed, lest thin lines and letter detail go missing, exactly as in the first example. |
| Zero999:
It's subjective to an extent. People differ in what they find clearest and easiest to read. Some like as higher contrast as possible, others prefer different coloured backgrounds. |
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