Oh Dear! I Just Fried My Whole Truck!!! - Page 3 - RC-Monster Forums

BrianG · 07.22.2006, 01:23 AM

Quote:

Originally Posted by neweuser

How do you solder them would be good info to pass. i would but never used them, but may help him too. And thanks Squee for the E!:018:

Diodes look like this. See how one end has a little silver band? That's the cathode, or negative side. You just hook them up like you would batteries; end to end.

+- +- +- +- +- +- +-

The power input would come in on the left and the load hooks to the right. Each one drops about .7v. There are other better ways to drop some voltage, but this is easiest IMO. Another simple way is to use a resistor, but the amount of voltage dropped depends on the current draw of the fan.

neweuser · 07.22.2006, 01:26 AM

Cool, that shold help him. Never had the need. So do you use them really when your running too many Volts?

BrianG · 07.22.2006, 01:53 AM

Quote:

Originally Posted by neweuser

Cool, that shold help him. Never had the need. So do you use them really when your running too many Volts?

Actually, diodes are intended to be used like a one-way valve; they only allow current to flow in one direction. However, they drop .7v each, and I use that fact to reduce the voltage. Only do this when the load current is small (<= 1A).

There are other better ways to drop voltage, but they are generally more complex and not as simple to wire up for those who have no electronics knowledge.

sjcrss · 07.22.2006, 09:08 AM

Hey NEWUSER.........hows the 12020 coming.......also the fan info was good guys.....I hope you get it fixed man.....

brijar · 07.22.2006, 11:06 AM

Thanks for all the fan info guys, but I have decided to just not use a fan if I get a new controller. I was trying to keep this whole fan deal cheap and just use a 12v fan I had lying around. What I should have done was asked if a 12v fan could take 16.8v. I ended up know that in the end.
I haven't e-mailed Mike yet, but it's Saturday here, so there is a good chance I will get to.

LOL, I started this thread to find out if there is any hope of getting my controller fixed, but you guys took off about how to wire a fan:D. Thanks for the info anyway. I will most likely ask you people before I go and try to wire something custom/different/weird/stupid up:007:.

Thanx a lot,
Brijar!!!

Sneeck · 07.22.2006, 12:34 PM

Sure a 12 volt fan can take 16,8 volt, it can take even more if you want to. It's just not going to live as long as normal.

I run a small 5 volt fan off of a six cell pack without any problem. Also no weird switches, just on 1 side of the dean plug(both + and -)

Sorry about your loss there, really suck's to loose every bit of electronic's in just a few second's.

squeeforever · 07.22.2006, 01:55 PM

Yup, its not that the fan can't take the voltage, but the fact that you sent 16.8 volts to the reciever as well as possible grounded out the ESC.

BrianG · 07.22.2006, 02:16 PM

Quote:

Originally Posted by squeeforever

Yup, its not that the fan can't take the voltage, but the fact that you sent 16.8 volts to the reciever as well as possible grounded out the ESC.

And sent 16.8v to the receiver pack...

Finnster · 04:13 PM

Eh, I still don't like that diagram, at least I would test it first beofre I put it with the rest of the electronics. What I don't see is a resistor in line with the fan. The fan and diodes should have some small resistance, but really it looks like you will just short out the fan/batts again. Maybe fans don't need R's? Not sure, but I wouldn't bet my esc on it.

What I would do it just tap a line right off the ESC where the input voltages go in (solder on top of the batt wire connection) and run it to the fan with a resistor (and diodes if needed.)

Here is a 12V 40mm fan It needs 120ma. So for 16.8V: (R=V/I) ~16.8V/0.12A=140 ohm. (150 ohm closest iirc.) If you use diodes to drop voltage you will need a lower R.

Note also that P=I^2*R. P=(.12^2)(150)=2.16W. You need at least that high-rated a resistor, or at least a combo of smaller resistors to do it. Ratshack has mini-resistors upto .5W, then bigger sandbar resistors.

If you do it this way, you don't need a switch to the fan, or long wires going everywhere. It will only turn on when esc is plugged in. You may switch your RX, but don't leave batts plugged in anyway.

Useful link with calcs

I would first do this with just the batts and fan. If you don't blow anything up, then integrate w/ $$$ escs. Or just get a 5v fan and a y-cable and tap off the rx and leave it easy...

G/L

Finnster · 07.22.2006, 04:22 PM

I would just get this and a y-cable into a RX. Easy, no fires, crying, etc..

BrianG · 07.22.2006, 04:34 PM

If he's gonna get a 5v or 6v fan, I'd just hook it to the AUX output of the Rx or use a Y harness off the Rx pack - no need for any diodes or resistors then. This would be by far the easiest solution. It's the dual speed thing that is making things more complex. Also, if he had a fan and had it running at its rated voltage, it would spin at a reasonable rate and wouldn't need a hi/lo speed switch.

BTW: Fans don't need resistors (are you thinking of LEDs?) The diodes will simply drop enough voltage so the fan doesn't spin so fast since he's running 16.8v to a 12v fan. At any rate, the fans internal circuitry only pulls what current is required, so no resistor is needed to limit it.

Finnster · 07.22.2006, 05:21 PM

Quote:

Originally Posted by BrianG

..

BTW: Fans don't need resistors (are you thinking of LEDs?) The diodes will simply drop enough voltage so the fan doesn't spin so fast since he's running 16.8v to a 12v fan. At any rate, the fans internal circuitry only pulls what current is required, so no resistor is needed to limit it.

Wasn't sure. It would be the same as plugging the fan right into the batt pack, not sure I'd want to just do that w/o testing 1st far away from my esc..

BrianG · 07.22.2006, 07:00 PM

Quote:

Originally Posted by Finnster

Wasn't sure. It would be the same as plugging the fan right into the batt pack, not sure I'd want to just do that w/o testing 1st far away from my esc..

Nope, that's perfectly fine as long as the current draw of the fan and the servos total is not more than the BEC, Rx pack, wiring, or switches can take (~3A). Mopst small fans are well under 1/4A so no worries there. Adding a resistor to the fan would be like adding a resistor to a servo - totally uneccessary.

brijar · 07.24.2006, 11:12 PM

I haven't recieved a reply yet to my E-Mail to Mike. Could someone tell me an average reply time for Mike? I'm kinda nervous, because this is a matter of life and death for my E-Maxx:013:, but I'm not asking him to hurry up or anything. I've never E-Mailed him before, so I wouldn't know how long it takes him to reply. He must get a lot of E-Mails each week, and that would be very difficult to deal with.

Thanx,
Brijar!!!

squeeforever · 07.24.2006, 11:22 PM

How many have you sent? Sometime it takes another email. I think reason being is because some of his emails might get filtered or sent to a junk mail folder. Try and send him another. He usually replies within hours.