Mr board current

[darthdan]

I read somewhere that the MR board puts out about 900ma at 4.5V. Can anyone confirm this? I am wanting to run a P4 that is on the way off of an Ani board, but they recommend keeping a constant current. I have a 1000ma buckpuck too. What is going to be my best option here?

Just run it straight off the board...

or

use the board and the puck (if so how to wire exactly?)

[Novastar]

How funny, I was JUST trying to confirm this over on the "MR saber versions" thread or whatever.

Here is some info that might help.

Most MRs have 64 LEDs, each rated at 20ma... Ultra states that this means they COULD be capable of 64 x 20ma = 1280ma.

However--I don't think the MR board shoots out so much--as you expect, and mention.

You're probably right about it being around 0.9A... and you are certainly right that LEDs are CURRENT hungry, and less voltage hungry. You need only get the LED over it's forward voltage and you're good to go.

A buckpuck would certainly help you to eliminate the questionable driving of the MR. Besides--as LEDs get better and brighter (thus requiring more amps)... using the MR to drive the light will NATURALLY become less effective.

For example, a Luxeon K2 Green *CAN* be driven at 1500ma. So far, the only board I know that can drive that... is Erv's... at 1.3A (1300ma).

[darthdan]

Right, but max current on the p4's is stated as 1 amp, so i'd be right on with the puck, i just need to know how to wire it all together. Or if I really need to. I know that moving from 900 to 1000ma is going to be brighter, but is it going to be noticible enough to warrant using the puck? Or just save it for another project?

I've got a DPDT, so I mean I could run the led through the puck on one side and the MR board on the other, but can I run both off the same battery pack?

If so can I just use a 4.5V battery pack and use common leads?

Does the MR board need to terminate? As in does there need to be something at the end of the circuit to avoid frying the board?

[neophyl]

Yes you can run both boards of the same power supply with the dpdt switch. Thats the exact same setup Ive got in my dooku sabre and it works fine. The charging port for the batteries acts as an overall on/off switch.

As for the MR boards current drive, well that can vary Ive found. Awhile ago I converted my Mace and put a white 3w led in there. I was never satisfied with the brightness and it only pulled around 600ma through it.

In an attempt to get it brighter I removed all the existing drive transistors and replaced them with a single logic level mosfet. As the mosfet has virtually no resistance (unlike the existing ones) its now brighter.

[Novastar]

Phil you're awesome. Awesome.

And bloody 'ell... only 600ma???!?! What the...???!?!? Yuck! What the heck version was that? Hmm, now I only wish I knew how much all the MR boards I'm running are shooting out. Although most of them seem ok.

This just goes to show that it's getting to the point where the MR boards... just aren't going to be ideal anymore as the single LED setups get better and can handle more juice/amps/etc.

Not surprisingly, I believe this will really bump up the market for sound/light boards than are non-MR.

God knows, the MR board is like... technology from 1999. Well, ok it was MANUFACTURED around that time. A Yusan spring shock sensor? Pretty weeny now...

[neophyl]

Well if you know a bit about electronics its possible to do some basic mods to the MR stuff.

The mosfet replacement I did is a bit like an electronic relay, you just tap off from the existing logig signals and it doesnt take up space like a relay or use as much juice.

The other potential future mod I considered while looking over the mace in detail was adding a low dropout regulator to limit the voltage to the MR board to 5v regardless of what voltage you input (as long as its 6v+). That would allow the use of higher voltage supplies that the 5w and other leds might need without endangering the board.

You can tie the positive supply of the led to the higher voltage and the mosfet would drive it quite nicely at whatever current/voltage you want via an appropriate resistor.

The other mod Ive done to a friends sabre was to add a driver (a corbin driver in this case) and use the MR board to trigger it. I couldnt use a dpdt switch as his sabre didnt use one and didnt have the room to fit one. So I used the same mosfet technique as it acts like an electronic switch to be the switch on the driver too. Now when the mrfx is switched on it switches the driver on too. Bit kore complex than just using the dpdt switch but i didnt have much choice.

None of the above are what Id suggest anyone else try as there is the potential to royally screw up your fx board. But for those with a bit of electronics training that know their components and how to identify them its not too difficult.

[Novastar]

Simply brilliant stuff, NeoPhil! Thanks...

Although I don't have a ton of electronics experience, I think I understand what you're getting at, which is that there are several ways to get the solution one might be looking for... which (in this case) is either a better way to make the MR drive the light (as LED innovation calls for it), and/or find ways to trigger what might "normally" be two circuits (i.e. Corbin + FX).

I would venture a guess that it's worth the experience even if someone fries ONE mr board. I mean, it's just ONE.

Besides, the technology is becoming old, old, old. That board design is as old as EP I. Still good, mind you... but... time for some UPGRADES!!

[Madcow]

Well if you know a bit about electronics its possible to do some basic mods to the MR stuff.

The mosfet replacement I did is a bit like an electronic relay, you just tap off from the existing logig signals and it doesnt take up space like a relay or use as much juice.

Great idea neophyl!
Would you be willing to put up some pics and or more detailed description of what you did here? I'd like to try it.

MC

[Novastar]

By the way, on an unrelated note, I've been testing Erv's v1.2 board with how long it can run...

GEEZ!

7.4 Li-Ion 2400Mah... with K2 green @ 1.3A...

it's been running for THREE HOURS... no decrease in brightness that I can detect, and still no PCB being tripped.

That's the longest (by far) I've ever had a saber run.

[neophyl]

Thats a very good run time and about what I expected. For me thats one of the true advantages to using a proper driver over a simple led, the much better run time when using above the minimum forward voltage.

Madcow, Im going to be wiring up a sabre this week and I have a maul board going in it so I'll take some pics and indicate where/how I wired the Mace up using them. Might take a few days though as theres a big event this weekend im preparing stuff for.