Changes by last author:
Added:
| * NO spare IGBT channels... Used all 8 on my coils so cannot directly apply [inductive pullup as described here] |
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* I don't have any IGBT channels to spare... Used all 8 on my coils.
** There's not enough drive from P259 to solve this - the necessary inductive loading would fry it all too easily. |
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* The P259 can handle the (appr 0.4A peak, 0.15A effective) current of the inductive pullup, but you need a 600V 1A .. 2A diode (ER2J or ES2J is fine) to protect the P259 output. An additional 200..400V bidirectional transient suppressor provides clamping
** ER2J cathode (marked with a stripe) connected to P259 output ** ER2J anode connected to inductor ** inductor connected to 22 Ohm 2W resistor ** 22 Ohm resistor connected to 1A fuse ** 1A fuse connected to +12V ** bidirectional transient suppressor diode connected *** one end to resistor (the leg close to +12V) *** other end to inductor (where the ER2J diode anode is also connected) |
| ** You can buy tacho adaptors to solve this exact problem - AutoMeter and MSD both make them. Of course I won't be doing this as where would the fun be then? ;) |
| Alternative options |
| ** The P256 simply isn't cut out to deal with inductive loads, so I have used an external transistor that will work with the an inductor/resistor pullup combination to drive the tacho. This may be integrated inside the tacho in due course as the tacho damping is playing up and it needs to be taken apart anyway... |
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* so I have used an external transistor that will work with the an inductor/resistor pullup combination to drive the tacho. This may be integrated inside the tacho in due course as the tacho damping is playing up and it needs to be taken apart anyway...
* buy tacho adaptors to solve this exact problem. The fun would be lost this way ;) |