Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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 _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
Fri Dec 10, 2004 8:10 pm
bigjimmy
Joined: 18 Jun 2004
Posts: 40
Location: New South Wales
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.
Sun Dec 12, 2004 3:12 pm
Spockie-Tech Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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) _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
Sun Dec 12, 2004 4:30 pm
bigjimmy
Joined: 18 Jun 2004
Posts: 40
Location: New South Wales
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.)
Mon Dec 13, 2004 11:18 am
Spockie-Tech Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
Mon Dec 13, 2004 11:36 am
bigjimmy
Joined: 18 Jun 2004
Posts: 40
Location: New South Wales
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?
Tue Dec 14, 2004 2:00 pm
Ajax Experienced Roboteer
Joined: 17 Jun 2004
Posts: 298
Location: Sydney
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. _________________ It's all about the destruction.
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