I'm A Noob - Page 1
Forum section: electronics / beginners

author: tony3d
author_rank: Frequent Contributor
timestamp: October 01, 2013, 12:51:35 pm
content: Ok want to make sure i'm right here. I take the arrows are pointing to the negative end of the capacitor on the right end correct? Really hate being a noob.

author: rdl
author_rank: Super Contributor
timestamp: October 01, 2013, 12:53:24 pm
content: Yes, because the symbol in the stripe is a negative sign (-). Be careful because sometimes the stripe will point to positive, then it will have a (+) marking.

author: c4757p
author_rank: Super Contributor
timestamp: October 01, 2013, 01:30:15 pm
content: Haha... I see axial electrolytics so rarely, I have to look twice too...

author: madires
author_rank: Super Contributor
timestamp: October 01, 2013, 01:56:42 pm
content: ... and the positive side got the groove.

author: tony3d
author_rank: Frequent Contributor
timestamp: October 01, 2013, 02:15:09 pm
content: Quote from: madires on October 01, 2013, 01:56:42 pmI guess the positive side of this one has a hole.

author: tony3d
author_rank: Frequent Contributor
timestamp: October 01, 2013, 02:18:54 pm
content: Thanks for the help everyone. I successfully transposed this from all alligator clips to my breadboard, and it oscillates between the two LEDS just fine, but can someone explain why my power supply jumps between Constant Current, and Constant Voltage with each relay flip of the relay? I can also hear the transformer in the supply flipping between two taps.

author: Dave
author_rank: Super Contributor
timestamp: October 01, 2013, 02:41:08 pm
content: When the relay state flips, the large capacitor gets connected to the supply rail. Because of the large capacitance and low ESR, it acts almost like a short (for a brief moment) and pulls a very large current from the power supply. The supply can't handle the current, so it momentarily switches to CC until the capacitor is charged up again. Simple as that.

author: Paul Price
author_rank: Super Contributor
timestamp: October 01, 2013, 02:48:17 pm
content: Be careful, some tantalum through-hole mounted capacitors and many types of surface-mount ceramic electrolytic caps have only a stripe that indicates the positive terminal of a capacitor.

author: tony3d
author_rank: Frequent Contributor
timestamp: October 01, 2013, 02:56:02 pm
content: Quote from: Paul Price on October 01, 2013, 02:48:17 pmThis one is indicated as (-). Thanks for the heads up!

author: tony3d
author_rank: Frequent Contributor
timestamp: October 01, 2013, 02:57:21 pm
content: Quote from: Dave on October 01, 2013, 02:41:08 pmThanks for the explanation. Would raising the current setting of the supply keep it in Constant Voltage then?

author: Dave
author_rank: Super Contributor
timestamp: October 01, 2013, 03:21:18 pm
content: I think raising the current limit would just shorten the amount of time the power supply is in CC mode. The ESR of these types of caps is usually really low, so you would need a very beefy power supply to handle that current spike without twitching at all.You could try adding bulk capacitance to the supply line or add a resistor in series with your capacitor, to increase the effective ESR, which in term limits the amplitude of the current spike. Try using something from 4.7 to 10 ohms.

author: tony3d
author_rank: Frequent Contributor
timestamp: October 01, 2013, 03:43:17 pm
content: Quote from: Dave on October 01, 2013, 03:21:18 pmThanks Dave I'll look into ESR a bit more. I'm having a blast with this stuff so far. I use be a CNC programmer/machinist. Loved to trouble shoot jobs, probably why I like this so much. Now I do 3D modeling and animation working out of my house for the past 15 years. This is a nice diversion.