Are FlexMod P3's still available or is there an equivalent that is ready to ship?

[flecom]

well from the picture it looks like an IRF part #

[polishedball]

Thanks Steve,

It's strange that he will not divulge the information as the pictures on the listing show the writing on the chip but just not clear enough to read it. It may be that when it arrives there will be nothing on it or it may have been removed prior to shipping.

We shall see.

- Neil

That is forum user BBe or something similar here on the board. He makes some nice parts.

[Bbe]

Neil, I told you all the information that would be required to calculate the heat sink area. You must start from the heat dissipation of the driver, then take into account factors such as air convection, etc. How to calculate the heat power - I told you. I bet that MOSFET datasheet will not help you in this.
http://www.vishay.com/docs/91172/91172.pdf

[Draco]

As i was reading this i found some one mention sanding off the part numbers to protect there design and for me that would be a turn off, it makes the driver unserviceable and hence a waste of money when they fail, i am an electronics tech and would rather service something then just throw it away, i have a very limited budget and can not afford the high priced controllers, unless it's burned to a crisp they can be repaired, one reason i like the P3 is it has some limited service options all though i never was able to find the 20 pin ball grid away, it mush be under something, most of the parts are off the shelf, i would love a kit for of the flex mod, say leave off the normal though hole parts and the solder on the more complext parts and take 5 bucks off, i also would love a schematic so i can at lest see how this item works. but if he filed off all the part numbers i would never by that product again, Unlike most of you i am on disability and cant afford a 200 dolor driver. I am grateful for DR lava's drivers, otherwise i would have no analog divers, all other ones are out side of my budget.


Hell if he meeded help building these i would offer my services, i have certification in smd soldering, i just lack a device for a BGA, thats the hard part to put on as pins are under the device and technically need an xray m,machine to inspect it

[Draco]

in fact on the original P3 i cant find a micro it all seems to be normal logic, it's the PCB that would be the expensive part if he offered in a kit for, and i only would want say a 10-5 dolor reduction or even less, i love building kits

The reason i would still want a driver for each diode is for field repair, one goes out it can be swapped out and repaired later, and all in one drive could cause a total failure, i know it makes it a lager device, but an 85-100 dolor driver blowing up as compared to a 35 dolor driver in my view is the better option, i also had a Chinese driver fail and destory my laser and the damned lasorb, i do not trust there crap.

Even the laser i repaired from a friend that was a few hundred bucks had to soft start and sent a voltage spike to the diode at every power on and shortened it's useable life.


I am hoping i can barter for some used P3, i dont need beam suppression so the older ones work fine

[neilhooper]

At the risk of upsetting someone.

Neil, I told you all the information that would be required to calculate the heat sink area. You must start from the heat dissipation of the driver, then take into account factors such as air convection, etc. How to calculate the heat power - I told you. I bet that MOSFET datasheet will not help you in this.
http://www.vishay.com/docs/91172/91172.pdf

I asked you via Ebay Ask a Seller a Question for the make and model of the MOSFET explaining that I would like to look up the datasheet to get the required information to enable me to make a calculation to be able to purchase a suitable heat sink. Instead of answering the question you replied and seemingly made an assumption that I don't know what I'm talking about. I already know how to make the necessary calculations for heat sink sizing. Your reply gave me a VERY simple formula to calculate the power dissipation for the MOSFET or as you call it, the heat dissipation. You also provided a link to a general google search page that returned a long list of websites about calculating the heat sink area. My reply to you pointed out that calculating the heat sink area is of no use to me as heat sinks are generally specified in ºC/W.

You replied with this :-

"Operating temperature range for most silicon chips - from -50C to 170C, with increasing temperature decreases the maximum power limit. I recommend not to overheat the transistor above 70C. In other words, I do not recommend using the maximum values for the calculation"

Feeling that I was getting nowhere I then turned to this forum where someone PM'd me with the details of the chip. I looked up the data sheet and found the information that I needed.

For everybody's reference the heat sink value can be calculated by using the formula,

Øsa = ((Tj - Ta) / PD) - (Øjc + Øcs)

Where
PD = Power dissipation (W)
Tj = Max allowable junction temp (ºC) (specified by device manufacturer)
Ta = Ambient temperature (ºC)
Øjc = Thermal resistance junction to case (ºC/W) (specified by device manufacturer)
Øcs = Thermal resistance, case to heat sink (ºC/W)
Øsa = Thermal resistance, heat sink to ambient air (ºC/W)

So as an example for this MOSFET which has a maximum junction Temp of 175ºC with Ambient temperature of 30ºC dissipating 15 Watts (Current*(Power Supply Voltage - Diode Voltage)) with a Thermal resistance, junction to case of 3.6ºC/W and a Thermal Resistance, case to heat sink of 0.1ºC/W the formula would become:-

Øsa = ((175-30) / 15) - (3.6 + 0.1) = ((145) / 15) - (3.7) = (9.66) - (3.7) = 5.96ºC/W

So you would choose a heat sink with a 5.96ºC/W or better. The lower the ºC/W value the better the heat sink. This formula assumes that there is no extra cooling and that the heat sink is in free air.

In fact this example is based on the heat sink that I'm going to need for my project. I have found one that is specified as 3.5ºC/W which is what I will be using together with a small fan. This will give me plenty of 'headroom' should I need to increase the dissipated power.

If you use your recommendation of not allowing the temperature of the MOSFET to go above 70ºC and substitute 70ºC into the above formula instead of 175ºC you will find that it's impossible to achieve as it results in a negative figure.

Of course this could have all been avoided had you just given me the information that I actually asked for in the first place instead of presuming that you know more than me; which I'm sure you do on some subjects.

I am not a person who is afraid to ask a question about something that I do not know or understand; I'm sure that Jordan from DTR will verify this as I've asked him a lot of questions in the last few weeks about diodes, modules and lenses, who, I must say, has been very patient and helpful.

Supplying drivers and other laser parts may or may not be your main form of income. If it is then I suggest that you brush up on your customer service. I am a small business owner myself and if I treated my customers this way then I wouldn't have managed 15 years in business.

I'd be interested to know what your "bet" would have been that the data sheet wouldn't help me.

- Neil

[swamidog]

many of us just bolt the mosfet directly to the aluminum baseplate in the laser projector. it's substantial overkill and takes less room.

[neilhooper]

many of us just bolt the mosfet directly to the aluminum baseplate in the laser projector. it's substantial overkill and takes less room.

That would be a good option but my project is not a projector. It is a proof of concept for laser etching. I only found this forum as I was searching for information and the search returned the following thread http://www.photonlexicon.com/forums/...-of-Grey-445nm and this driver will probably be housed in an enclosure about 100mm x 100mm x 100mm and made of plastic.

Interestingly enough I remember seeing a graph somewhere a long time ago that showed how using bigger and bigger heat sinks doesn't make much difference after a certain size which also suggested that you would need some sort of forced air cooling to help.

So with that in mind bolting the MOSFET to the baseplate may not be enough in some situations, but then I know nothing about projectors

- Neil

[polishedball]

Perhaps there was is a language barrier. Are you communicating in Russian or English with him via eBay. Just saying that could play into it.

[Bbe]

Increasing the heat dissipation also gives a negative C/W. What is surprising, the results of actual measurements have nothing to do with the results of this formula. I am inclined to think that Øjc value has no practical application because in the datasheet is not shown actual value, max only.