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nead a high speed transistor

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Screech

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I nead a faster power tranny.
The ones I'm using seem too slow. :(

With 1 transistor, I'm trying to energize 6 loads at 4 Amps in total, in about 2 milliseconds.
Iv'e used different transistors and it seems some are slower then others.
Am I better off using 6 transistors driving 1 load each?

Is the "Ft Mhz table" for transitor on/off times?

When using the same transitor ,will it take a longer time to turn on at a higher current ?

I nead a fast tranny @ these loads. <Where to find these specs.
Are smaller tranies faster then big ones?

Thanks all. :(
 
Screech said:
I nead a faster power tranny.
The ones I'm using seem too slow. :(

With 1 transistor, I'm trying to energize 6 loads at 4 Amps in total, in about 2 milliseconds.
Iv'e used different transistors and it seems some are slower then others.
Am I better off using 6 transistors driving 1 load each?

Is the "Ft Mhz table" for transitor on/off times?

When using the same transitor ,will it take a longer time to turn on at a higher current ?

I nead a fast tranny @ these loads. <Where to find these specs.
Are smaller tranies faster then big ones?

Thanks all. :(

2mS is an extremely slow switching time, any transistor is going to be massively faster than that.

I would suggest you probably need to increase the base current substantially - perhaps you could post the circuit for comments?.
 
here.
It's an injector driver.

I've added enough base current to give 6 amps when there is no load(load replaced with multimeter).
With load connected it only gets 3.8 amps.
With transistor bypassed the loads passes 4.12 Amps.

Transistor used is 2n3055 (to3)

when I use an mj15003 (t03) it seem to energize quiker.
Car idles richer for the same pulse width.
 

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Screech said:
here.
It's an injector driver.

I've added enough base current to give 6 amps when there is no load(load replaced with multimeter).
With load connected it only gets 3.8 amps.
With transistor bypassed the loads passes 4.12 Amps.

Transistor used is 2n3055 (to3)

when I use an mj15003 (t03) it seem to energize quiker.
Car idles richer for the same pulse width.

You didn't show enough of the circuit :lol:

We need to see the driver arrangements, it still sounds very much like you need to increase the base drive substantially. A 2N3055 if a very low gain device, to staurate it you really need to hammer some current into it's base!.
 
Why not try a Mos-Fet. Its Voltage controlled.

Not Current Controlled and It will give you a Higher drive current and not the .6 volts collector to Emitter voltage of a transistor.
 
chemelec said:
Why not try a Mos-Fet. Its Voltage controlled.

Not Current Controlled and It will give you a Higher drive current and not the .6 volts collector to Emitter voltage of a transistor.

A MOSFET is a good idea. You will not need to worry about how much current goes into the base. The minimum ON-state loss is generally lower. If very high base current is used, you can get it down to a 0.3v drop on any bipolar, but it has to be overdriven fairly high. MOSFETs only have an ON-state resistance, some parts are 1 ohm, others are only a few milliohms.
 
However, you will have to ensure that your gate-drive can supply the peak-current since the input of a FET is effectively a capacitor. If you have a too-low a current capability the FET will turn on slow
 
One of the problems that is difficult to overcome is that current builds up exponentially in the injector because of the L/R time constant. Do you know the inductance and resistance of your injectors?
Check out **broken link removed**. It says typical turn-on time is 1.5ms. Sounds like you aren't too far off on your target. How fast (slow) is your transistor? I agree that a MOSFET is probably a better solution.
 
Screech said:
I've added enough base current to give 6 amps when there is no load(load replaced with multimeter).
When you replace the load with the multimeter, the transistor has about 12 volts Vce. Its beta will be much higher than it is when it's saturated (with maybe 300-400mv Vce). You need to hammer the base with at least 400ma to get good saturation at Ic=4 amps. You can buy logic level MOSFETs to do this, but be aware that you still need high drive current capability if you want to switch fast, because the effective gate capacitance is very high.
 
I'll give it a good HAMMERING today.
Will probably take all day cause I got to put the fuel rail and manifold bits back on the car.

The injectors are about 16 ohms each, wired in parallel.
Long injector cables lower the current !
I'll try to keep them as short as possible.

Ok, I'll try mosfets in the future if i still have troubles. I just dont know anything about them yet.


Thanks for your replys. :D
 
I put 1 Amp into the base, but still have the same problem.
I'll put more tommorow.

I even used two power supplies, 1 for the controller and 1 for the injector driver.

I built the below Exhaust Gas Oxygen Meter.
Red= lean
Green =perfect
Yellow = rich

While driving I can adjust from lean to rich.

But when idling ,It is always rich(see pic).

If I try to leanen it, it starts to miss fire, as if some injectors are not energiseing. It will show green, but I guess thats because there was not enough fuel injected to ignite, (oxygen present in the exhaust).

When in Drive "D" @ idle,it will not miss fire as it does in Neutral, at same pulse width. Revs will be slightly less in "D". I wonder if the little bit of load in gear helps to ignite the fuel better.


The cars original computer has no problen idling in the grean and red section at idle :? I think it is batch fired too. It uses two banks of 3 injectors.

Tomorow i'll put 2 to 3 amps into the base.
I doubt it will have a different effect.

If you haven't worked it out yet, I'm using my own design computer & injector driver.
 

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Like I said, I would use a Mos-Fet. Probably an RFP50N06. Thats a 50 Volt, 60 Amp Fet.
You would only Need ONE, Mounted on a suitable Heatsink. And Since I would Think you have close to 12 volts drive to the gate, (You haven't shown the drive circuit) But Almost no current is required. Definately in the Micro-Amps.

This Device has an ON Resistance of .028 Ohms, Resulting in Negatable Loss.

Gary
 
Thanks Gary,
I will try to source that Mos-fet.
Thanks for that part number too.


I drove the car last night.
It felt perfect , but my meter tells otherwise.

:D
 
Hi Gary, I sourced the fet.
Do you know wich pin is the gate etc?
I know nothing about these devices.
Can A multimeter work that out?

Thanks :)
 

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Is this how to use it?My pic is probably wrong. :?:


is the gate the same as a base on a tranny?.
is the Drain the same as a collector on a tranny?.
is the Source the same as the emitter on a tranny?.
 

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Screech said:
Is this how to use it?My pic is probably wrong. :?:


is the gate the same as a base on a tranny?.
is the Drain the same as a collector on a tranny?.
is the Source the same as the emitter on a tranny?.
Yes to all three..
the main difference between a fet and a bipolar Transistor is the FET turns on with a voltage as someone else stated..
i dont see how one could pump 50 A through a TO 220 package though.. but thats what the spec says..?
 
williB said:
Screech said:
Is this how to use it?My pic is probably wrong. :?:


is the gate the same as a base on a tranny?.
is the Drain the same as a collector on a tranny?.
is the Source the same as the emitter on a tranny?.
Yes to all three..
the main difference between a fet and a bipolar Transistor is the FET turns on with a voltage as someone else stated..
i dont see how one could pump 50 A through a TO 220 package though.. but thats what the spec says..?

For short pulses I would guess. I don't think you could get that sustained, since that's (pulls out calculator) 70 Watts.
 
The picture is wrong.

I bought that fet, and tested it as a transistor.
It didn't work as one!

After thinking it was faulty, I thought it may be digital, as it only has an on and off.

I wired it up digitally and, Yep, It now works properly. Its neads to be triggered as a digital component.


Are all fets to be wired as digital?
and bi-polar trannies as analog?
 
Screech said:
The picture is wrong.

I bought that fet, and tested it as a transistor.
It didn't work as one!

It wouldn't, it's not a transistor, it's an FET - try testing it as an FET!.

After thinking it was faulty, I thought it may be digital, as it only has an on and off.

I wired it up digitally and, Yep, It now works properly. Its neads to be triggered as a digital component.

It needs to be connected and driven correctly, nothing else!.

Are all fets to be wired as digital?
and bi-polar trannies as analog?

No, either can do both equally well, but you can't just interchange them - the circuit configuration required is different, as is their method of operation. As already mentioned, a transistor is current driven, and an FET voltage driven.
 
As I sad before, I don't know how they work.
The pics that I found on the net don't work.

So I tryed the following and it works.
 

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