Strobie Boards

Hey guys. Quack here.

This board was initially designed to be a spike killer of sorts, but upon further testing and research they do NOT perform as intended, and as such they will be repurposed for PWM, and also potentially as a switch bypass of sorts.



Here's the pinout of the driver. The blank square via is the PWM in pad (there's proper labeling on the new, smaller boards).

They measure 6.56 mm by 7.13 mm.

Here's a video explaining the new purpose:


Used a 555 timer on the gate of the MOSFET and it works pretty well. Above certain frequencies though it seems the capacitance on the mosfet starts to cause some problems and limits the upper frequency range use. Very little heat is produced by the board.

These are designed to go between the battery and the driver.

Re: The Diode Savior (aka spike killer)

Subscribing, sounds very promising! :beer:

Re: The Diode Savior (aka spike killer)

Sounds good Keep us updated.

:beer:

Re: The Diode Savior (aka spike killer)

I like where your head is at! Excited to see how it turns out ,,+1 :beer:

Re: The Diode Savior (aka spike killer)

I think you'll run into problems when the driver tries to send constant current into what is (initially) an open-circuit. Seems easier to add soft start into the driver itself. A properly designed driver won't have spikes to begin with, anyway.

Another problem I see is that the cap will only discharge to the lasers forward voltage, or the fet's Vgs (whichever is larger). I think. So the second soft-start will be a lot less soft.

Re: The Diode Savior (aka spike killer)

Cyparagon said:

I think you'll run into problems when the driver tries to send constant current into what is (initially) an open-circuit. Seems easier to add soft start into the driver itself. A properly designed driver won't have spikes to begin with, anyway.

Another problem I see is that the cap will only discharge to the lasers forward voltage, or the fet's Vgs (whichever is larger). I think. So the second soft-start will be a lot less soft.

Click to expand...

When the driver sends current into the circuit it'll be pushing it primarily through the cap; The MOSFET I'm planning on using has an extremely low turn on voltage, only like -2 volts.

So, as soon as the gate reaches -2 volts the MOSFET will be on fully and the laser diode will turn on as it should. The driver wouldn't know the difference (since the laser diode would essentially be an open circuit prior to reaching its forward voltage anyway).

And I guess I'm a lil confused what you mean by second soft start.

Re: The Diode Savior (aka spike killer)

When power is removed, the cap will retain charge.

Re: The Diode Savior (aka spike killer)

Cyparagon said:

When power is removed, the cap will retain charge.

Click to expand...

True, I suppose. Seeing as it'll be a relatively small value cap though the internal resistance of the cap should be (hopefully) enough to discharge it, at least enough to make it useful again.


We'll see how testing goes. Bought the parts necessary and some violet laser pointers for testing purposes.

Re: The Diode Savior (aka spike killer)

https://www.youtube.com/watch?v=tPc3edYSDyU&feature=youtu.be

Proof of concept video.

Re: The Diode Savior (aka spike killer)

https://www.youtube.com/watch?v=dlHO2_x9ONA&feature=youtu.be

Got the boards today!!

Played around with the resistor values a bit; I think I found a sweet spot for it, but I don't have any drivers for testing these at higher currents.




Would anyone be willing to try testing these out, scoping them (using a digital scope, I only have a CRT one) and checking them out? Naturally you'll be able to keep the board if you so want. I'm mainly concerned with testing them with higher current drivers and whatnot; depending on how these perform I may have to limit them to just lower current builds.

Re: The Diode Savior (Super Soft Start)

This looks like an interesting idea. There
is a way to discharge the capacitor quickly
when power is removed. It may also be
better to connect this ahead of the driver
instead of connecting it between the diode
and driver.

Re: The Diode Savior (Super Soft Start)

Some interesting preliminary testing done today.

I whipped up another LM350 linear CC-driver, and set it at some various points with my soft start board in between the driver and the diode.

Tested it with both a normal test load, and one of those phlatlight red LED's from the projectors.

So, the interesting bits;

The higher the forward voltage of the diode, the lower the amount of heat generated by the board is. i.e, when using 4-5 volts, the board generates nearly zero heat.

When used with a phlatlight, that has a forward voltage between 2-3 volts, the board generated a GREAT deal of heat. I'm positive this is due to how P-channel mosfets operate. Since P channel mosfets are considered "on" when the voltage between the source and the gate is more negative, having LESS voltage on the outputs means the mosfet doesn't turn on completely, generating heat. The higher the forward voltage, the more the mosfet turns on (until it's saturated) and then it generates nearly no heat.

I measured the voltage drop between these two scenarios; When using a phlatlight, at 1.8 amps, the board dropped nearly 0.556 volts. 1 watt dissipated in the tiny little mosfet (which, surprisingly the mosfet held up fine. I ran it for a minute and nothing ever broke.).

When using a test load and setting the forward voltage to 5.5 volts, the board dropped less than 0.1 volt at 1.8 amps. Less than a quater of a watt lost.

The boards also maintained their soft start characteristics during both of these scenarios; the phlatlight -faded- on, and the oscilloscope showed a soft start when using the test load.

These boards MAY have to not include the red high powered diodes we use, unless you heatsink the transistor on the board with your driver.


The Lightning Stalker is going to receive 3 of these soon, so he can do some testing of his own with various driver types. I'm quite sure the results will be the exact same, though but I want to be positive before I start selling these.

Re: The Diode Savior (Super Soft Start)

I see another problem (unless I'm misinterpreting your setup).

Part of the reason some drivers overshoot is that the current sensing doesn't really kick in until the driver is close to its target current. This is the case for a couple reasons. Often the current sense ICs take their power from the driver's output, and thus won't kick in until the voltage curve gets up to the IC's requirement. Also they often have minimum voltage drop sensing requirements, and drivers are designed to work as close to those minimums as possible, to stay efficient.

So that's all to say that the spike is often a product of the fact that you're not up and running yet. So drawing out that startup process by artificially restricting current flow seems like a bad idea.

Not to overly simplify matters, but why would you not simply add two or three really good ceramic caps? That doesn't delay regulation (because charging them doesn't interrupt the driver's intended operation).

Re: The Diode Savior (Super Soft Start)

rhd said:

I see another problem (unless I'm misinterpreting your setup).

Part of the reason some drivers overshoot is that the current sensing doesn't really kick in until the driver is close to its target current. This is the case for a couple reasons. Often the current sense ICs take their power from the driver's output, and thus won't kick in until the voltage curve gets up to the IC's requirement. Also they often have minimum voltage drop sensing requirements, and drivers are designed to work as close to those minimums as possible, to stay efficient.

So that's all to say that the spike is often a product of the fact that you're not up and running yet. So drawing out that startup process by artificially restricting current flow seems like a bad idea.

Not to overly simplify matters, but why would you not simply add two or three really good ceramic caps? That doesn't delay regulation (because charging them doesn't interrupt the driver's intended operation).

Click to expand...

I'm almost positive that the current spike problem is gone since I've changed the values of the resistor; and the soft start board acts honestly no different than a laser diode, aka, an open circuit until you reach a certain voltage and then it starts to conduct/turns into a closed switch (which is around 1-1.5 volts). Of course though like I've said, I've sent some to Lightning for additional testing to make sure that there's no spikes created through its use. I've thought out the way it works in my head, simulated it several times, played with the values a great deal and I really think I've hit the sweet spot between a visual change in how the laser starts up and no spike issues.

I'm thinking that the effect it gives is also a really cool point, since it looks really cool vs the instant on all lasers currently have.

Re: The Diode Savior (Super Soft Start)

Le Quack said:

I'm almost positive that the current spike problem is gone since I've changed the values of the resistor; and the soft start board acts honestly no different than a laser diode, aka, an open circuit until you reach a certain voltage and then it starts to conduct/turns into a closed switch (which is around 1-1.5 volts). Of course though like I've said, I've sent some to Lightning for additional testing to make sure that there's no spikes created through its use. I've thought out the way it works in my head, simulated it several times, played with the values a great deal and I really think I've hit the sweet spot between a visual change in how the laser starts up and no spike issues.

I'm thinking that the effect it gives is also a really cool point, since it looks really cool vs the instant on all lasers currently have.

Click to expand...

Right...but that doesn't address any of my points re how your device is likely to interact with an actually switching driver.

Again, what's the benefit to this over just a couple high value capacitors? I think that's the better approach.

Re: The Diode Savior (Super Soft Start)

rhd said:

Right...but that doesn't address any of my points re how your device is likely to interact with an actually switching driver.

Again, what's the benefit to this over just a couple high value capacitors? I think that's the better approach.

Click to expand...

Because in order to get the long drawn out start that this board currently has you'd have to be using physically large electrolytic capacitors and somehow shove them into your builds.

This board is effectively recreating a very large electrolytic cap while only being 8 mm x 8mm in size. I totally understand what you're saying with how it would interact with a switching driver. However the MOSFET starts fully conducting when the voltage difference is only 1.5 volts, +-0.1 volts, and laser diodes don't start fully conducting 3+ volts.

What we're worried would happen is if we're using a boost driver, for example. Current starts to flow through the board, to the cap, and the P channel mosfet turns off. Voltage begins to build up (up to about 1.5 v) P channel mosfet slowly starts to turn on, voltage slowly drains through (anything excess is burned off as heat, since it's the linear zone) and the laser diode starts turning on, until full current output is achieved and the MOSFET behaves like a closed switch. At no point in this should anything over what the laser diode can handle reach it since the turn on voltage of the mosfet is below what any laser diode can conduct. And any spikes would be removed early on through the mosfet's linear phase.

Aka, the driver shouldn't know the difference, linear or otherwise. And I AM going to make sure that it's NOT going to be murdering any diodes before I try to sell it to anyone, please, don't worry about that.

And as I've said I'm gonna be pushing the soft start effect as a selling point ALONG with the spike killer aspect of it.





Not to mention this is just a little idea I've had. If no one wants to use them that's perfectly fine, they're only 3 component boards, and the components in them I'm going to be using for other purposes anyway. I've been itching to make boards and stuff for lasers again and this is, I think, a good way to get back into it.