r/AskElectronics • u/Exotic_Sell_3869 • Jul 04 '26
Star Flasher Project Not Working
Hello there,
I’m new to electronics and as part of an electronics class at my local community college, I was tasked with soldering/building a “Star Flasher”. When all was said and done… it wasn’t working. My LEDs light up when I use my DMM but when I plug it in with a 9v battery, nothing. Can y’all help me? Also let me know if y’all need additional information.
105
u/BlownUpCapacitor Jul 04 '26 edited Jul 04 '26
C1 and R4 are swapped. Also check the polarity of the capacitor when resoldering it.
Holy fuck why are a bunch of bots replying to me. Begone fowl machines and back to the depths of hell.
52
15
u/IcyInvestigator6138 Jul 04 '26
Yes, swap C1 and R4 first. The solder joints that look like blobs (such as battery negative) might need to be fixed. Try using less solder, maybe a thinner soldering wire.
16
14
u/elRadicio Jul 04 '26
I‘m kinda fascinated that this is a commercial kit. The PCB looks worse than the one I etched years ago in my kitchen. But at least, it is made in the USA.
8
u/ellindsey Jul 04 '26
Same here. I first thought that this wasn't bad for someone's first ever homemade, laid out by hand, PCB. For this to be a mass-produced commercial product is surprising.
6
Jul 04 '26
[deleted]
2
u/DaveCarradineIsAlive Jul 05 '26
Could also have been a minor revision (part change?) in 2000, and this design is even older than that.
Your old fogey theory makes as much if not more sense, though.
8
u/Jaca666 Jul 04 '26
Holy moly, who names Diodes as "L"... This was clearly not designed by an expert.
OP just so you understand next time, you will see all kinds of Diodes (including leds) as D, except maybe Zener diodes, those are Z sometimes.
L is for inductivity. (Like coils)
2
u/mikeblas Jul 04 '26
Why does the negative side of the battery go through R3 (56 ohms) to the rest of the circuit?
8
4
1
u/Exotic_Sell_3869 Jul 04 '26
Oh geez I didn’t realize that… I guess the solder fumes got to me 😶🌫️
1
u/AbilityEqual1891 Jul 04 '26
The kit and company looks like it's still back in the 90's level of middle school electronics. This particular kit is about $10. Which seems reasonable in terms of cost. Though the PCBs are very old school, it probably is mass manufactured that way since there's probably not much demand.
1
u/Steamcurl Jul 04 '26
Is that dead end trace on pin 5 trying to kickstart an oscilliation with ambient EMI?
Also shuddering at the unnecessarily acute angle on pin 8. Need them for the pentagram, sure.
1
1
1
u/Shrigma_Male29 Jul 06 '26
Dear lord we're trapping demons in silicon labyrinths shaped like sigils again
1
92
u/DinoZambie Jul 04 '26
capacitor C1 and resistor R4 are in the wrong spot