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FET switches
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how many amps do you want to switch
5
0%
 0%  [ 0 ]
10
0%
 0%  [ 0 ]
20
11%
 11%  [ 1 ]
30
11%
 11%  [ 1 ]
50
33%
 33%  [ 3 ]
100
22%
 22%  [ 2 ]
150
0%
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200+
22%
 22%  [ 2 ]
Total Votes : 9

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Spockie-Tech
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Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia


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The HIP chip used in the IBC performs 4 functions..

It senses the voltage on and drives the high side of the H-bridge, acts as a fast-charge driver for the gate capacitance on the Fets, controls the anti-shoot-through timing between the low and high side switching and has some simple logic to help the micro in driving the right fet with a single PWM output (oh and braking as well).

To replace all of those functions with discrete logic is a major pain in the bum, which is why most H-Bridges use it or something like it.

If you were to use P-Type FETs on the high side of the bridge you can do without the high-side gate sensing and charge-pump driver, but you just cant get P-Type Fets with anywhere near as good current handling capability (for the $) as N-Type fets for some reason.. (something to do with the atomic crystal lattice structures and the P-Type doping having less free electrons I think).. you would still need the timing, gate charge and logic though
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Post Fri Dec 10, 2004 8:10 pm 
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bigjimmy



Joined: 18 Jun 2004
Posts: 40
Location: New South Wales


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Ok then so can someone expleain to me how to hook these chips up then? (or a link to a site?) They dont sound to hard to use. Its just that everytime I look at something about these chips, there always like 100 page data sheets.

Post Sun Dec 12, 2004 3:12 pm 
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Spockie-Tech
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Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia


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If you dont want to read the data sheet and understand what its all doing (which is quite a job) then just copy the HIP Drive circuit from the IBC (which is based on the OSMC design).

The circuit diagram is in the manual PDF (at the bottom of the IBC page on the robowars site)
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Post Sun Dec 12, 2004 4:30 pm 
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bigjimmy



Joined: 18 Jun 2004
Posts: 40
Location: New South Wales


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Can I drive them from a PICAXE micro (I dont have an amtel programmer)
what do I have to put into the HIP chip to control the H-bridge?
Also, what is the number for the HIP chip used in the IBC (it doesnt say on the Schematic.)

Post Mon Dec 13, 2004 11:18 am 
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Spockie-Tech
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Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia


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In theory you could drive a HIP H-Bridge from a PicAxe.. some of the PicAxes have constant PWM outputs (the 18x's and above I think), although there will be limitations you will have to deal with, for example only the larger PicAxe's (28+ IIRC) can ouput more than 1 PWM output simulataneously. You will need to check the datasheets on that.

The HIP chip used in the IBC is a HIP4081A.. to Drive it, you need 3 signals (per bridge) from your controlling micro - a PWM speed input, a direction input, and a disable (brake) input.
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Post Mon Dec 13, 2004 11:36 am 
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bigjimmy



Joined: 18 Jun 2004
Posts: 40
Location: New South Wales


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The PICAXE 08Ms have PWM output. Does the PWM frquency (or is it duty cycle or something?) have to change depending on the position of the stick or can it just be the same all the time?
Where can I get the HIP chips from?
If you do need a PWM frequency that changes, what commands would I have to use to tell it to change the PWM according to the pulses from the receiver?

Post Tue Dec 14, 2004 2:00 pm 
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Ajax
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Joined: 17 Jun 2004
Posts: 298
Location: Sydney


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The 080M has 2 PWM commands "PWM" & "PWMOUT"

The one you what to use is "PWMOUT" this is a true PWM command. the other is a mickmouse version.

The command is as follows

pwmout O/P pin, period, dutycycle

With the 08M the 'O/P pin' has to be 2 (it is the only pin that supports PWM)

If you set the period to '249' this = 4KHz (255 = 3.9KHz)
Decreasing the value will increase the frquency

And vary the dutycycle value.

Remember that the 'period is a byte (ff Hex = 255 Dec)
and the 'dutycycle' is a word (ffff Hex)

So if your using the pulsein command you will ned to make a calculation to get the full use of the dutycycle.
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Post Tue Dec 14, 2004 6:18 pm 
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