- Circuit components from Farnell turned up. Excellent business ! Will definitely buy all future components from them, unless I need them in under 24 hours. Brilliant supplier. Much better than Jaycar.
- Next order, will get LM338 but in TO-220 package, not TO-3 (and try to get it to work better). Don't want to be beaten by the LM338.
- Checked the Forum for responses on the shunt charger circuit. Yes, all good.
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- Got a BD682 (PNP transistor) to replace the BD681 (NPN)
- Installed in circuit ... doesn't work.
- It seems the PNP transistor needs to be raised to the +ive rail it is switching, in order to turn it off.
- So if trying to switch using a 555 ... which raises and lowers to its own rails ... then it isn't possible to completely switch off the BD681.
- This is a particular limitation applying because the 555 output toggles between its own rails.
- This does not apply to a NPN transistor, which can be turned off by simply driving it to ground, and then turned on with its simple threshold voltage (which, from memory, I think is 2.5V or something).
- Interesting lessons. I am going to have to re-create the Kart Control circuit.
