Serin serout problem

[lerameur]

I have a big ass heat sink, about 9 times he size of the chip.
I believe I was under th wattage recommended (or maybe just on it, cause the battery was fully charged at 12.85 and @ 1.9 amp 24.7 watt.
would that of killed it.

I looked at comse circuit for making my own H-bridge, but is seems a bit messy.
I have some IRFZ44N N mos, maybe get their brother P's and work with that, you have any schematic ?
I found this: http://www.armory.com/~rstevew/Publi...d/nch-brdg.htm
but I dont know


update:
I tried one IRFZ44N , it become very hot with just 5watt. I know I can put a heat sink, but this thing is suppose to support 94 watt. Is there somehting I am not getting ??

[lerameur]

to go back to my LCD problem , I am not using backlight. I thought you where refering to the contrast adjustment. nothing is connected to th backlight supply. IS this ,my problem , From the other post you mentionned, The gentlemen did not have a problen and the backlight was not connected. Mine does.

[skimask]

I have a big ass heat sink, about 9 times he size of the chip.
I believe I was under th wattage recommended (or maybe just on it, cause the battery was fully charged at 12.85 and @ 1.9 amp 24.7 watt.
would that of killed it.

I looked at comse circuit for making my own H-bridge, but is seems a bit messy.
I have some IRFZ44N N mos, maybe get their brother P's and work with that, you have any schematic ?
I found this: http://www.armory.com/~rstevew/Publi...d/nch-brdg.htm
but I dont know


update:
I tried one IRFZ44N , it become very hot with just 5watt. I know I can put a heat sink, but this thing is suppose to support 94 watt. Is there somehting I am not getting ??

Well, like I said, the only way something can dissipate heat is if it has resistance in the first place, zero ohms across a device = zero volts dropped across it = zero watts dissipated in it. If that MOSFET is a standard MOSFET, and you're driving it with 5v, it isn't going to work very well. You need a logic level MOSFET, one that's designed to be driven with 5v. And monster heat sinks only work well up to a point. You can only get rid of so much heat so fast, they got limits too.
Why not post a schematic...we'll get a better idea of what you're up to. (on a side note, I haven't gotten over to the L298N datasheet yet).

[lerameur]

well eventually I would like to use 15v at 2 amps, so that h-bridge might to be ideal for now.
To follow your idea on using MOSfet, I found a web site talking about the IRF540, which is very similar to the one I have IRFZ44N., Except they use Pmos also, I guess I can use 4 Nmos and using an inverter instead of using 2 Nmos and 2 Pmos.

[lerameur]

what about driving one L298 per motor instead of two motors ?
will it be creating less heat ?

[skimask]

well eventually I would like to use 15v at 2 amps, so that h-bridge might to be ideal for now.
To follow your idea on using MOSfet, I found a web site talking about the IRF540, which is very similar to the one I have IRFZ44N., Except they use Pmos also, I guess I can use 4 Nmos and using an inverter instead of using 2 Nmos and 2 Pmos.

You got it, for the most part. In the end, you get 2 control lines, one for on/off, and one for direction. But, you will have to use 2 N's and 2 P's and an inverter (which you can also use a couple of small MOSFETs and a couple of resistors and make your own inverter from components rather than a 7404), N channel on top, P channel on bottom. Remember (in basic terms), N channel MOSFETs work by applying a ground to a circuit, P channel's apply power to the circuit.

And yes, some snubber caps and protection diodes, just in case. Motors are ugly in some ways...

[lerameur]

I put back the circuit together with one L298.
added caps, Its really hard to make them stick onto the motors, any thoughts?
Also it was not working at first, I realized that my Pic chip was not putting some pins at high. I changed the program so the pin output went from portC to portD and it worked. I reprogrammed the chip a few times, those couple of pins on PortC are not working no more. Can I revived them ? what happened..

[skimask]

I put back the circuit together with one L298.
added caps, Its really hard to make them stick onto the motors, any thoughts?
Also it was not working at first, I realized that my Pic chip was not putting some pins at high. I changed the program so the pin output went from portC to portD and it worked. I reprogrammed the chip a few times, those couple of pins on PortC are not working no more. Can I revived them ? what happened..

Post your circuit, otherwise it's hopeless...

[lerameur]

basically I am driving the h_bridge directly from microcontroller. Some one told me to use an opto coupler. BUt the output of the microcontroller is hooked up to the enable of the h-bridge, how can that fry my pins. I just fried my ccp pin..
Also, would it be better to use a seperate power supply for the controlelr and h-bridge?

[Archangel]

I have a big ass heat sink, about 9 times he size of the chip.

Sounds good, how about some "B/A" bypass capacitors, or snubber diodes to protect those transistors, motors throw off some outrageous spikes which may well cause your bridge to get "Kentucky Fried".

what about driving one L298 per motor instead of two motors ?
will it be creating less heat ?

Always better, I think.