BroMikey's Capacitor Dump Circuit

[Farmhand]

Going by the schematics on the previous page, Bromikey seems to be using a high side switch between the caps + and the battery +, he would be better served to use a low side switch between the battery negative and the cap negative. That would simplify the driving circuitry.

If he has the mosfet drain at battery voltage he will have problems without a working level shifting driver circuit or something. I'll ask him.

Cheers

[Farmhand]

I've just recently downloaded the newer manuals for the picaxe chips and it tells me now that the M2 chips can all run at the default clock speed of 4 Mhz or they can be clocked up to 8 -16 and 32 Mhz, the old manuals only stipulated that the M2 chips could be clocked to 8 Mhz. Theoretically the M2 chips at 4 Mhz clock speed can output a 500 Khz PWM signal,
but at 32 Mhz the theoretical PWM signal could be 4 Mhz. Not bad for a cheap 8 pin micro.

What I like about the smaller chips is the price, the small size and low power draw along with many of the functions of the larger chips. For more outputs and inputs the 14M2 seems good and I intend to use those more.

..

[MarkE]

I've just recently downloaded the newer manuals for the picaxe chips and it tells me now that the M2 chips can all run at the default clock speed of 4 Mhz or they can be clocked up to 8 -16 and 32 Mhz, the old manuals only stipulated that the M2 chips could be clocked to 8 Mhz. Theoretically the M2 chips at 4 Mhz clock speed can output a 500 Khz PWM signal,
but at 32 Mhz the theoretical PWM signal could be 4 Mhz. Not bad for a cheap 8 pin micro.

What I like about the smaller chips is the price, the small size and low power draw along with many of the functions of the larger chips. For more outputs and inputs the 14M2 seems good and I intend to use those more.

..

An alternative 8 pin part is the Atmel ATtiny85.  64MHz PWM oscillator, ~$1.00 each.  The core runs 8MHz, 8MIPs.

[Farmhand]

Mark those chips look awesome, I scanned this document below and found a lot of interesting functions it can do. And the price is much better than picaxe, however. How long would it take me to learn how to write code for it. I'm a complete novice, the way I see it trying to learn how to write programs for picaxe is difficult enough, and I also want to learn how to use Arduino.

Is there a language I can use to program them all ?

It has some good PWM features.

http://www.atmel.com/images/atmel-2586-avr-8-bit-microcontroller-attiny25-attiny45-attiny85_datasheet.pdf 

..

[SeaMonkey]

BroMikey's self-education project continues to reveal to him
interesting developments just when he thinks he's got it
figured out.  His education has progressed to the point
where he "knows enough to be dangerous."

Not meant to denigrate BroMikey or his endeavors but it is
a phase that all aspiring electronics technicians work through
as they grow in their understanding.

Six paralleled MOSFETs should be more than capable of handling
40 Ampere pulses, or even more, if properly driven and properly
protected from flyback pulses which are capable of destructive
avalanche of the MOSFET Body diode.

Hopefully BroMikey will either find the answers to his dilemma through
his own research efforts or a knowledgeable tech will provide him with
the elusive technical details he hasn't yet found.

It is possible in his case that his MOSFET gate driver chips aren't properly
positioned as close to the MOSFETs as possible and with sufficient capacitance
to properly drive the Gates.

It is also possible, and very likely the case, that the length of the cables from
his capacitor bank to his battery bank results in quite a lot of stray inductance.
At the instant pulsing current switches off a very substantial flyback pulse will
be generated which, although very brief, will take the MOSFET's into avalanche.
Since avalanche characteristics are quite different amongst the parallel connected
MOSFETs it is probable that one of them will serve as a current hog for the avalanche
current.  In time this will destroy the MOSFET and result in its failure much as has
been the case so far with his setup.

Thankfully, these problems are rather routine in high current switching systems
and the remedies are well established,  BroMikey will find success if he keeps
searching.