Power Functions Motor Interference

[dsjove]

I think I just blew my capacitor

[mattallen37]

Normally you can't really "blow" a capacitor. Unless you reversed or way over voltaged it, it should'n have blown. Also, unless it physically changed (bulged or literally blew up), it is likely fine. Why do you think yours blew?

[nxtreme]

Could you post a photo of the capacitor? Doesn't have to be super high quality or anything, just showing what it looks like. But yes, capacitors can blow up. I should have added a sentence about that... . You don't have to worry about the polarity of ceramic capacitors (in your circuit, the .1 uF cap), just the voltage . And you usually don't have to worry too much about that either 'cause they're usual rated above 25 V. Anything rated for at least 16V should work.

Electrolytic caps (the 33-100 uF cap) are polarized, meaning that if you get it reversed it will most likely blow up (as you have witnessed ). They usually come with a white stripe down one side, next to one of the wires that comes out of it. That side (or wire) of the capacitor should connect to Gnd or 0V if your more picky about using terms correctly. And you need to get a capacitor with the correct voltage ratings. Well, at least not the wrong ones . You need to pick a cap that has a similar voltage rating of the circuit your using it in along with at least 60-70% extra overhead. Example: 5V circuit, get something that is at least 9V: 10V circuit, get something that is at least 16V and so on.

The reason for this extra bit of overhead is that manufacturing allowances sometimes mean that a cap rated for 16V will only work to 10V before blowing up. I assume you've already figured out which wires are which in a PF cable, if not go to Philo's wonderful website. However, if you're still using a RCX cable, be sure you don't accidentally reverse the voltage by reversing the orientation of the connector. Sorry again for not explaining everything correctly the first time 'round, hope I did better this time . And don't hesitate to ask more questions if you don't quite understand something yet (or if I didn't explain it correctly), as I'm sure you'd rather be safe than sorry when it comes to a $40 dollar camera...

[dsjove]

I am new to this stuff and was incorrect. Capacitors are actually fine. I have since spliced a PF cable. A solid state relay is being used, enabled by the PF cable, so camera will always get correct polarity. I'll post once it is all wired up. Thank you.

[dsjove]

All wired up! The capacitors are doing their job better than expected. I threw in a relay to better control the camera. Unfortunately I couldn't find LEGOs the correct size to contain the items, so it is all electric taped. Thank you all for your help!

[nxtreme]

Great to hear that it's all working! Also good to know that the cap didn't blow, they can be nasty sometimes. Do you have the relay setup so you can control it from the remote? Sounds pretty cool! I don't know how big the circuit is once it's all put together but you would probably be able to fit it in a project enclosure. If you live in the States, Radioshack sells them (in other sizes as well) and, considering the quality of most of their other electronic bits and pieces, they aren't that bad. If you don't live in the States you should still be able to find something that'd work, like Steren in Mexico or The Source in Canada and Farnell in Europe and Australia. Or, you could just wrap it in tape .

[dsjove]

I was able to fit a bridge rectifier in a 2x2 brick. The dremel was involved . The end result looks like the PF light cable. For the camera circuit, I'll need a 2x4x3 brick. Until I get one, tape works!

The relay is used so the variable lines can switch the constant power lines to the camera. No varying polarity or voltage issues on the camera.

[nxtreme]

Sounds like it turned out looking nice! Ahh yes, a dremel. Almost as useful as some well place dynamite (or gunpowder) . Using the relay along with PF just gave me some ideas... . Well, good luck and have fun building!