Here is an idea.. not that I don't think you are building it right or with strong enough transistors.. and maybe this will compromise integrity. How about slots that would allow the owner to insert a fuse that once inserted would jumper from to source to gate on each channel? Last ditch 'stuff happens' emergency repair measure without having to do hardware re-wiring in the field.
put me on your PM list when you have a final-ish block. Currently using: WR250R w/heated gear, 12VDC in tank bag for cell+GPS; sometimes charging vidcam. Big fan of your work, rock on! Have you heard of the various crowdfunding sites, if you need to tap the social network for startup funds ($25K)?
Software guy here, not hardware so excuse the stupid question. Will any of the features mentioned allow me to control my heated grips like a heattroller(sp ??)? If so, will I be able to attach a rotary type switch to do the controlling, or will I need to whip out my smartphone everytime I want to change the temperature?
New thought on a feature. - Ability to sense voltage and adjust/trip circuits as user programs. Two examples: 1) Sense the voltage to tell if bike is running or just key is on. How used? Glad you asked. In case of HID lights. Do not turn them on until the bike has started, saves the ballast from suffering through sags in the voltage during starts. Below 13.6 volts, don't turn on the circuit. But once on, leave on till bike is turned off or user selects off, latching need in case of situation below. 2) Shed a load when voltage drops. How used? Have some circuits, like those on the PWM side used for heated gear, go to a lower level or shut off completely if the voltage drops down while engine is running. Like when you pull up to a stoplight and have to idle. Running voltage starts dipping below 13, start shedding loads. Matbe set the load shed up with priority, allow user to select to turn off heated gear before LED's, or pants before jacket before grips before gloves... T
Voltmeter is already in the design. Example 1 is on the list already, example 2 is interesting and will be considered.
I don't think knobs are necessary for this. The system is designed so that you can use a momentary button to change a circuit between preset duty cycles (read temp levels). So you can cycle between say, 0%, 50%, & 100%. The indicator LED will blink telling you the circuit affected (by color) and the duty cycle selected (by blink speed). Like the single channel board in the attached video. <iframe width="853" height="480" src="http://www.youtube.com/embed/MPtUWEFvfoU" frameborder="0" allowfullscreen></iframe>
Cool. Saw you were adding in the voltmeter part (since it is already on most PICs/processors) didn't know you were adding it into the user programmable part, but good. Much better then just using a delay timer function. The load shedding would be nice, I've done it with analog discrete designs, but it's a pain. Looking forward to the final... will let you get back to it... if I don't come up with some more dream list things. T
That would definitely compromise the integrity. When you see how these are built, I think you will be pretty confident in it. A lot of testing will be done as well. Its a two board design, the power board will contain a ton of copper for current capacity and thermal mass. The prototypes have 12oz of copper foil but I will build them for production with at least 24oz of copper foil as well as a bus bar and I will wave on piles of molten tin on the bottom as well. The controller board is a standard PCB but I've put a lot of energy into clamping transient voltages so that the semiconductors don't get grenaded. If I'm not confident these things are robust, I'm not going to build them because they are going to cost me just about all I have to build them in enough quantity to make them affordable for you.
I was just more thinkng along the lines of computer glitch, voltage spike, or severe impact takes out the cpu or a transistor just has a case of early mortality. Having some way that could allow the user to bypass the FET's on a particular channel and just feed power full on through. At first I thought of a dip switch, but they wouldn't handle the amperage. So then I thought maybe fuses could be used as an emergency jumper/splice into a recessed slot. And by using a fuse you save your own hide in case that channel died from an overdraw of current. And as I write this.. I'm thinking that I could always just build myself a bypass kit (short piece of wire with a fuse holder, high amp and a low amp fuse) and carry along. Not that I don't trust you...
The FETs I chose can handle current spikes above 1400A. That is not a typeo, one thousand four hundred amperes. They can each handle 100A constant current and there are 8 and I will limit each to 15A. These power FET's will not be blown up by anything short of armageddon. They have incredible temperature characteristics as well. My main concern is the load switches blowing up due to transients but I've got clamps all around them so I think they will survive. Time will tell.
Can you limit the current flow on each FET channel? Can it be user programmable? In the right appliation... use it as a build basis for LED drivers that limit it... and then I could use that to test how far I can push an LED on overdrive.
It will be setup like a circuit breaker. The user will, via their phone, set the maximum current allowed per circuit (each circuit has it's own current limit). I'll give it a a time characteristic like a fuse so it can over current for a few seconds before shutting down. The plan was to then require the user to reset it via the phone of by cycling the bike power. There is no reason why this circuit couldn't be a constant current supply as well. I'd have to check the speed at which I can query the ADCs effectively. If I can set it up so that you can have a circuit auto reset indefinitely that will give you a constant current supply. You won't get a circuit breaker in that case though. I am doubtful of the performance of the ADCs to think this is possible. We will just have to see.
Would be cool if possible, and that would be the preferred method for proper LED dimming, vs pwm. But I'll take a version either way. If the constant current works then we could eliminate the buck pucks/drivers from our LED ligts and save a few percentage points if efficiency. And make building your own lights, or upgrading lights, mucho easier.
The constant current waveform will just be a PWM waveform. If I were setting this up, I'd use a current limiting resistor to protect the diodes and use the standard PWM signal to dim them. That may be obvious as I always design these things with myself in mind as the first customer. I don't know what a buck puck is but I assure you the only thing you need to run LEDs other than this box is a current limiting resistor setup so that the maximum current allowed through the circuit is <= the max through the LEDs.
Sorry.. a buckpuck is a name brand of a LED constant current driver. Name just kind of means generic constant current to the DIY led community now. A buckpuck is when your supply voltage is higher the the forward voltage of the leds, a buckboost is a current limiter and voltage booster used when your supply voltage is lower then the leds required forward voltage. A quick run-down of what I was referring too.. So a resistor will limit current, but only a specified amount at a specified voltage. Has to be calculated each/every time. Increase voltage and the current flow can increase too. A buckpuck (aka constant current supply) limits the supply but lets voltage float, upto an amount that is slightly less then the supply side. With a constant current supply there is no need for the resistor to limit the Led. As long as your string of leds have a forward voltage less then the supply, you can control their brightness by limiting current. If forward voltage is greater then supply, you can still limit current but the led's will not achieve max brightness. If you pop open a high quality led light you won't find any current limiting resistors in line with the led's themselves. Using a resistor to save an led from runaway is an inexpensive way to do it when you know the supply voltage and have limited amounts of low light leds. But when you start talking high power led's, varying voltage supplies, resistors would not be a very efficent way to go. Now you'd have to worry about the heat the resistors generate and your losing supply power to that resistor, killing your batteries faster then necessary. Plus as the batteries drop voltage when they age the led's will dim since available current will drop due to the resistor being a fixed value. Again, resistor, cheap and easy for small led, constantly wastes energy, not effective for high power. Onto the variable part. Using pwm to flash the led's on/off faster then we can see is one way to dim them. There is where I have seen some pwm (dimmers) cause problems. The buckpuck or buckboost (ie the led driver) does not like the frequency that the dimmer is using. Not real common occurrence, but it happens. Low powered led's that are using resistors for current limit don't really care about the current being pulsed. But if you can just flat out limit the current, and by varying the current you adjust the brightness, it's even better and ultimately more efficient. Clear as Mississippi mud? and more then you wanted to hear?
I am familiar with the idea of constant current. I guess I just fundamentally disagree with the common knowledge. The definition of a constant current is a constant voltage through a constant resistance. Therefore, using a resistor to limit the current is no more inefficient than using a constant current supply as the resistor doesn't use extra current, it just limits it which is all the active constant current circuit is doing. What it DOES do is require you to set the resistor to a conservative value or risk blowing the semiconductor during transients. This actually means that on average you should use less power with a resistor compared to a constant current supply. The cost of this will be the max brightness you can attain. So, if the complaint was that you need all the light possible and a resistor leads to LEDs being too dim, I'd buy it. Efficiency, I am not buying. Personally, I don't worry about maximum brightness. I'm putting on the aux lights because my main light is a giant steel grill in front of it to protect it from flying rocks and its covered with mud so I can't see the damn road until the next river crossing. If I was really concerned about max brightness I'd not ride in the mud. My system does NOT boost the voltage so you will have to concern yourself with forward voltage drop if you have too many LEDS in series. I also doesn't do any voltage regulation (short of cutting out transients above 18V). My system therefore would not allow you to get "maximum" life span and "maximum" brightness out of your LEDs but they are still going to be damn bright and you will be able to control them from your phone from the campfire when you want to see what just flew into your can of Dinty Moore stew. This will all be irrelevant if I can get a fast enough data feed from my current sensors to create an active constant current supply. If I can, I'll short out some wires on video and post it up for all to see. Then, I'll send you a virtual beer for the fine idea.
This is a report on constant current function requested. It works relatively well for moderately low resistant circuits. In this test I have a 10Ω load and it works very well, albeit a lot slower than an analog constant current supply. So, while my concerns about speed were well founded this is a reasonably useful way to control constant currents. Will this feature make it into the final design? I'm not sure... If I thought constant current was vital, I'd prefer to do it in the analog domain which is generally faster than doing things digitally. Is this a reasonably useful feature? Yes. It does still require that you add a little impedance to the circuit to prevent your LEDs from popping (because of the speed the circuit reacts), but much less than required without any constant current control. <iframe width="640" height="480" src="http://www.youtube.com/embed/Keq5Q5_pY6Q" frameborder="0" allowfullscreen></iframe>
Example showing interactive use of the constant current mode with an iPhone. <iframe width="853" height="480" src="http://www.youtube.com/embed/86zFWAr7ptU?rel=0" frameborder="0" allowfullscreen></iframe>
