Re: Sow how are they making one go 300ft plus?

by teslaguy on Sun Dec 07, 2008 6:09 pm

this most likely is a very foolish question, but i was wondering if it was possible to stack multiple leds on one transistor on top of each other on the board. I thought that i could do this by decreasing the resistors by half (for 2) or by 2/3s for three and henceforth. I would also place a much larger capacitor on the board to store the extra power that the additional leds would use (i have an extra 1 farad 7.2 volt laying around), and might use some very high power 3000 nicad rc car battery cells. so if i was to stack lets say 4 leds on top of each other in each of the slots (on a magicsoft board), what other alterations would be necessary and what type of fets would i need to replace the transistors to supply enough power? thank you very much.
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Re: Sow how are they making one go 300ft plus?

by Amberwolf on Mon Dec 08, 2008 12:31 am

As long as the transistor you are using can handle the total power across it for the duration you are placing it under load, you can put as many LEDs as you like across it.

I recommend using series-strings of LEDs if you have a higher voltage you're starting with, so that as much power as possible is going into the LEDs and not across the resistor and transistor.

If you choose to use parallel LEDs, use separate resistors for each one, rather than a smaller resistor for all of them, so that you don't have to worry about differences in the LEDs' forward voltages causing the ones with lower voltages to rob the ones with higher voltages of their power.

If you are pulsing LEDs and transistors with VERY short bursts of power at low duty cycles, and don't actually exceed their absolute maximum ratings, you can even leave out any dropping resistors, which ensures more power thru the LEDs and less wasted in-circuit. But if you do this you should try to calculate out and/or measure the voltage drops across the LEDs and transistor(s) so that they take up the full voltage provided to them, with little or none leftover.

You don't have to use FETs instead of regular Bipolar transistors, though since it is an on-off application the FETs will probably be more efficient. If using FETs, the RDSon value and the Gate-turn-on voltage (and charge) are two of the most critical values you need to select them by, as well as the actual maximum D-S voltage and current.

There are some automotive LED driver chips from Maxim and others that use FETs designed for the purpose of driving LEDs for markers and turn signals, as well as interior lighting, and some of them can even do buck/boost on the supply voltage to keep the levels perfect for the LEDs to keep them always at the same brightness (forward current). Most of them are surface-mount, though, so keep that in mind when designing with them.

Remember when using larger capacitors that the inrush current to charge them at first will be significantly higher, so any component in the path of that inrush current needs to be able to handle it.
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Re: Sow how are they making one go 300ft plus?

by teslaguy on Mon Dec 15, 2008 12:53 am

thank you very much for your very informative reply. I actually have an extra led driver from maxim that i purchased during my last arduinome project. I might order a board for it. I have a larger problem right now though. I ordered a New Magic Inc Extra High Powered TV-B-Gone® Remote and built it, and it works, but the problem im facing is that it continually cycles through all the codes, the momentary switch will reset the microcontroller but if i do not repress it, it will act as if it has been repressed anyway after its done. I dont see any solder bridges, and i checked all the components with my multimeter. they all work. I also tried placing a new microcontroller in it that i flashed but that had no effect either. the jumper is in the correct position and i dont see any bugs, does anyone have any idea what could be the problem? The voltage fluctuates between 5.5 and 6.1 volts when its on which i think should be about normal. Ill get back to you guys if i prototype one with my MAX7219CNG+ND. well thanks again guys.
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Re: Sow how are they making one go 300ft plus?

by SolidSilver on Mon Dec 15, 2008 9:13 am

teslaguy wrote:I ordered a New Magic Inc Extra High Powered TV-B-Gone® Remote and built it, and it works, but the problem im facing is that it continually cycles through all the codes, the momentary switch will reset the microcontroller but if i do not repress it, it will act as if it has been repressed anyway after its done.

That's actually the intended behavior for the stock firmware on the EHP. I reflashed mine with caitsith2's firmware to solve the issue.
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Re: Sow how are they making one go 300ft plus?

by teslaguy on Tue Dec 16, 2008 7:11 am

ahah, I wasnt aware. thank you very much. I might reflash mine as well. Next time im going to have to do some reading before I post.
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Re: Sow how are they making one go 300ft plus?

by srvctec on Mon Jan 19, 2009 1:01 am

Earlier this week I ordered a EHP kit from Ben and received it yesterday. Got it put together last night and it works great! I just got through ordering from Mouser an enclosure that will (hopefully) hold the circuit board and batteries. In case anyone's interested, the part numbers are 635-H-65AC-B and 635-2105IR. It's a case and IR window that should just hold everything nicely.

Now for my questions. I went through this thread, but haven't really found the answers, since it seems everyone already knows what they are doing in regards to programming this thing.

1. How do I get all 209 codes into the chip (the EHP doesn't turn on/off my tv in my office)?
2. How do I install firmware?
3. What do I need to install the firmware?
4. Where do I get what I need and how much will it cost and where's the best place to purchase?
5. What are the two red LEDs for- just to let one know that the device is sending codes or is there another purpose?

I should also mention that I received a version 3 TV-B-Gone last week, but just had to have much more power.
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Re: Sow how are they making one go 300ft plus?

by srvctec on Fri Jan 23, 2009 11:37 pm

Anyone care to help a newbie with this?
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Re: Sow how are they making one go 300ft plus?

by The_Don125 on Sat Jan 24, 2009 3:13 pm

To put a new firmware into the chip, you need an AVR programmer. Probably one of the more convenient ones to use is Ladyada's USBtinyISP, costs $22 + shipping.
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Re: Sow how are they making one go 300ft plus?

by srvctec on Sat Jan 24, 2009 3:50 pm

The_Don125 wrote:To put a new firmware into the chip, you need an AVR programmer. Probably one of the more convenient ones to use is Ladyada's USBtinyISP, costs $22 + shipping.


Thanks. Looks like this programming stuff is way over my head. I'm excellent at the hardware (20+ years as an electronics technician), but haven't programmed a thing before- I leave that up to programmers. So I guess I'm stuck with what I got in the EHP kit. Getting ready to put my kit into the case I mentioned above.

Edit: Completed single enclosure for EHP and 4AA batts. here.
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Re: Sow how are they making one go 300ft plus?

by ubestbsteppin on Wed Oct 19, 2011 6:13 pm

Does anyone have any of these boards still around? I'd like to buy one if you do. Thanks.
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Re: Sow how are they making one go 300ft plus?

by exapod on Tue Feb 14, 2012 12:56 pm

I wanna make this board and power it with a 3,7 V Li-ion. What resistors i need to use for the base of the transistors?
Sorry for my english
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Re: Sow how are they making one go 300ft plus?

by blark on Thu Aug 15, 2013 1:38 pm

Just wanted to let you guys know that I just ordered 10 of these boards from seeedstudio. Prices have come down a lot in the last few years so for $15 bucks shipped I can get 10 boards, what a steal!

If this first round is successful, I will probably mod the board to use SMD components, and configured the LEDs to emit in 270 degrees and do a new run. Fun stuff thanks everyone for your work and keeping the original Eagle files online. Much appreciated!
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Re: Sow how are they making one go 300ft plus?

by blark on Thu Mar 20, 2014 8:05 am

Hey oPossum are you still active here? I'd like to ask you a question about the transistor configuration used here. It seems this forum does not allow PMs..
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Re: Sow how are they making one go 300ft plus?

by oPossum on Fri Mar 21, 2014 5:02 pm

I am subscribed to this thread. What do you want to know?
I am the Possum, and I approve of this message. Sent from MacBook Wheel Sorry for my bad German.
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Re: Sow how are they making one go 300ft plus?

by blark on Mon Mar 24, 2014 5:24 pm

oPossum wrote:I am subscribed to this thread. What do you want to know?


If you wouldn't mind, I kinda stole your design for my Raspberry Pi IR gadget. The post is over here: viewtopic.php?f=8&t=51433

I am trying to figure out exactly HOW to estimate the resistor values I need, and some other questions. I'd certainly appreciate your input on the matter!
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