Gentlemen: I have all of my FSBUS cards built and working. I have only one question. Does anyone have an idea of a way to get more than 1.2 volts from the led connections? The 1.2 volts are too low to adequately light up an led. They are just too dim. Any help would be appreciated. Milt

There is no way as they are multiplexed.Only possibile option is for Dirk to design a new board with latches.But it would be a lot more complex (and costly) then the present one.A workaround is available on my site (down this message), it involves some soldering and some transistors.The ones described in the article are for high power devices (such as incandescence lamps), for use with low power devices, such as LEDs, you can use low power transistors.

If you want "more power" for lighting LED's or lamps, isn't there a simpler way??? For example, change the BC377's on the original FSLED card to higher gain and higher current transitors (like your BDX53 darligton's) and then add more "powerful" transitors ahead of the current limit resistors (again like your BDX53 darligton's) that have a more powerful collector source and then adjust the current limit resistor to whatever brightness you like. You would need a lot less components if it was done in a scheme like that. Also, I have a side question about the schematic??http://www.cockpit-italia.com/modules.php?...article&artid=9Looks like the BDX54 will get turned on when then the "common" pull down transitor is "active" and you apply BAT voltage minus the Vce sat voltage to one end of the lamp, but shouldn't the emmiter and collector be swapped on the BDX53? Also, how is the "BAT" referenced to the PIC?Gus

>If you want "more power" for lighting LED's or lamps, isn't>there a simpler way??? For example[...]Unfortunately not: the FSBUS method is to use the PIC itself to give power to the LED array, and use transistor to connect the ground.>Also, I have a side question about the schematic??>>http://www.cockpit-italia.com/modules.php?...article&artid=9>>Looks like the BDX54 will get turned on when then the "common">pull down transitor is "active" and you apply BAT voltage>minus the Vce sat voltage to one end of the lamp, but>shouldn't the emmiter and collector be swapped on the BDX53?>Also, how is the "BAT" referenced to the PIC?You are right (must be the first to really look at that schematic...): i have swapped Emitter and Collector on both transistors. The scheme should be Common Emitter...Well my fault, i'll correct it.As for the BAT: as explained in the red lines, it is just a way to depict a power supply with the ground in common with FSBUS and the positive whatever you like.For example you can use a PC PSU: the 5V lines power the FSBUS while the 12V power the lamps.Inside the PSU the 5v and 12v grounds are the same and interlinked to the common ground.That's what i tried to conceil in the text.Thanks for pointing me to the error in the schematics.

I'm suggesting to buffer the signal from the PIC with an emitter follower (with a large Hfe and it's own voltage source) to drive the FET's/lamps and a "higher gain & current" transistor for the common grounding transistor on each "connector bank". Why wouldn't that work?? I can't think of an electrical reason unless it's hard to get high gain transitors with enough bandwidth. If that is the case, you could just use a MOSFET.What have I missed that wouldn't allow this to work??Gus

>I'm suggesting to buffer the signal from the PIC with an>emitter follower (with a large Hfe and it's own voltage>source) to drive the FET's/lamps and a "higher gain & current">transistor for the common grounding transistor on each>"connector bank".I'm sorry but i just can't follow you: i have no idea what an emitter follower is, let alone the Hfe (although i have a vague idea).Maybe there are buffers that could use the "ground active" signal from the PIC to latch the rows...But even so, what's the advantage?You'd always need another 2 transistors...Only advantage i see, is the fact that the luminescence of the devices would in that case be constant, while in the normal FSLED system it is not as the delay between each scan depends on how many channels are on.Anyway i am sorry but my electronics knowledge is low, i'm just a beginner: this month i've started Electronics 1 which teachs the basics of BJTs and, next month, FETs.For now i am only managing electrons and holes, reverse currents, common base, and the likes.What i know of circuit design is selfthought without theory.I can follow you, but i'd need some clarifications ;)

The original post asked about providing more voltage/current for LED's . Actually, 1.2V should be enough to light the LED. It's probably a case of not enough current to give the desired brightness, in which case you would want to reduce the 100 ohm resistor to increase the current, but you HAVE TO BE CAREFUL. The PIC can only source or sink 25mA per pin. That is the current level you wouldn't want to exceed. As you point out, the scheme as it was originally designed relies on the PIC for power, which is limited. If you wanted to increase the available power, your circuit will work, but it adds transistors for every LED/lamp. The FSLED card has 4 banks of 8 LED

I would like to see a schematic of this as well.Claudio and I have had a similar discussion some time ago when I wanted to run panel illumination from the led card. I chose a different method that time.I would like to see your method.If you can save the schematic as a jpeg, just attach it to your post when you reply.RegardsDavid

DavidI can't save it as a jpeg. I can copy it as a bitmap image into a word document. If you can view MSword files I'be happy to send it to you. I have not built this circuit and tested it, but it's a pretty basic circuit and "should" work just fine if the proper transistors are selected. If the desire is to only control 5V lamps and LED's then a couple of MOSFET's (one N-channel and one P-channel) could be used as well. MOSFET's have the advantage of VERY low on resistance. The only problem might be with the available current from the PIC to drive the gate capacitance to switch it on and off fast enough.Gus