Recent blog entries for rsbohn

Symet work continues. Built a FLED solar engine on a 8 pin DIP socket. This way I can swap out the resistor as needed. I'm using 4 salvaged 3300 uF caps from a defunct motherboard and a motor from a junked cassette player.

Pulled two stepper motors and a circuit board from an old dot-matrix printer. I need to work out a driver circuit for the stepper motors.

Got sample LM7121 chips in the mail. These are for an amateur radio project.

Got my LP339M samples in the mail: 4 low power comparators in a 14 pin SOIC narrow package. Wasn't sure it would be possible, but I managed to free-form a light seeker circuit right on the tiny chip. I ganged the comparators so I could sink more current (hope for 60 mA) on each side. I used 2 220K resitors for a voltage divider and two LDR's for the light detectors. After several retries I had the circuit assembled. I plugged it into the solderless breadboard, connected a limiting resistor and two LED's. No smoke! Unfortunately my LDR's weren't balanced, I had to embed one of them in clay to make the circuit work better. Blinkenlights! Just waving your hand in front of the sensors will make it switch side to side. I think this circuit would be fine for a simple light tracking headbot. Hope to post some pictures soon.

Got a $1 solar calculator from WalMart. I get 1.5V from the solar cell at the batery connectors. WooHoo! I'll have to go back for a dozen more. Sure beats the $4 I paid RadioShack for 0.55V.

Working on a FLED solar engine. Since I just had the 0.55V clinker I was trying to run the thing on 2 D cell batteries. My motor (salvaged from a 35mm camera) started up with 3V, seems like the speed changed as the FLED fired and the light was flashing on and off :*( . Tried different resistors, no luck. So I put in a pot voltage divider. No luck with that. The 'always on' range overlapped the 'wailing like a banshee' range. So I'll try the new power cell (from the above calculator), but I may need to find a different motor (hmm, got another camera at home...)

Oh yeah, 250V can give you quite a jolt! Be careful if you open a camera with a built in flash!

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