Team Eventorizon: Build Diary

[overkill]

No issues, but is your secondary weapon meant to sear our retinas off? That's 3W of light in Binky...

[Eventorizon]

Ummm... its just 12V strip LED lighting. Its not meant to be crazy powerful but... I don't know. Really, 3W.

Seems that plan is shot anyway, the parts are not back in to RS until the end of next month and Farnell don't stock them.

EDIT: Is it safe to wire the lights up to just 1 of the packs in the set used to drive the weapon? It would mean the draw was fractionally unbalanced by about 1/4 of a Watt but it would bring the Voltage down to something that I can deal with more easily.

[overkill]

Google the part number; I'm sure I saw some other UK sources.

It probably depends on how you are charging the packs. If you charge them separately, then they will balance out and everything will be fine. If you charge them in series like they were one big pack, then its possible the pack running the LEDs will not get a full charge before the other pack is full. It would still be OK if you balance the packs after charging them

[Eventorizon]

I charge them separately as we only have a 6S charger. When you look at the maths, the LED strips draw 400mA over 1m and I am using less than half that. 200mA in comparison to the idol rating of the motor 2.24A its less than a 10th, and the draw when its spinning the weapon its probably nearer 20A so 100th. In 3 minutes I can't see it off balancing the packs enough to damage them.

Anot other thoughts from people? Have I missed any options?

[Mouldy]

I have put as much electrical tape as I can on the cable. Yes, I aught to use grommets but you have to buy them in box's of 500 off RS and the tape worked well last time.

And no worries Dave, I know you meant well. That said I can't get an LED on the weapon side of the power system cos everything I have put in there has been cooked by the high voltage so I hope Binky wont get failed for that. Drive has an LED though so hopefully that is enough.

Simply put Alex no LED = failed tech check.

[Max]

Just put 2 24v LEDs in series as Dave said, each one will only get half the voltage so dissipate half the power. It worked fine when I had 2 12v LED strips running off 24v.

You could do as you say and run the LED off just one of the packs, you could then do the same with the other pack with another LED so they both get drained about the same.

[Eventorizon]

Would same principal work if I used 4x 12V LED strips? I don't have any 24V LED's and I don't want to keep going out and spending more and more money when I have parts that already work.

That said I have found a 48V LED which would light up the machine like a christmas tree.

EDIT: If I put a pair of 18 ohm 3W resistors in parralel to the same LED what do I get? The resistance should be the same but the number of watts it can deal with should go up to 6W. Am I right?

[Max]

EDIT: If I put a pair of 18 ohm 3W resistors in parralel to the same LED what do I get? The resistance should be the same but the number of watts it can deal with should go up to 6W. Am I right?

No, total resistance drops to 9 ohms due to:
1/Rt=1/R1 +1/R2 ...

[Eventorizon]

Ok... I don't want to be playing silly games with resistors so that out.

I can get a 48V LED in with a 2.7 Ohm 3W resistor but with a maximum current of 1A it will be producing 48W of light! Cooling it isn't an issue as I can use the chassis as a heatsink but 48W of light is insane. However because its so simple its very tempting, I just worry it will put even more strain on the batteries.

If its 1A at 48V the is it drawing 1A/h? If so I can live with that.

[RobotExtreme]

1A is always 1A no matter voltage, mean if you have a charge of 1A during one hour you have 1A/h, but this is capacity that battery will need to supply.

How will you have 48W passing across a resistor of 3W??

To us, if you have 1A in 48V you is wasting 48W to show your robot have link in?? This is more than a RS550 in continuous work. Redesign this, use a single led 1W with a resistor of 2.5kohm.