Moderators: Dave Moll, Steve Anderson
Harry Dalek wrote:How fine a voltage adjustment is needed half the time? Most circuits are 5 or 12 volts...
Steve Anderson wrote:True, but often I'm tasked with something that needs to work over a range of voltages, say from a battery supply. So the device may be used with a small 'brick'-type 9V battery (UK PP3, US 6LR61), however you want a reasonable life out of the battery. Say a 'give-up' voltage of 6.5V, by then the battery is considered exhausted.
For mains-powered devices I have a Variac, the item might be designed for a nominal 240V but I check that it still meets specifications at 200V (which covers 220V countries) and doesn't catch fire at 260V (e.g. Malaysia can often have a supply of over 250V). Pro-rata 120V countries, especially parts of Japan. Japan is divided into 120V/60Hz and 220V/50Hz regions, though some prefectures are still on 100V!. Though with switched-mode supplies (e.g. a laptop) it doesn't matter, 90-250V, 50/60Hz.
I think I've solved the open-circuit pot problem, now I need to add some current limiting/short-circuit protection. It won't be as simple as the LM317/337 arrangement above, but not overly complex either.
Steve A.
Some battery dis
Harry Dalek wrote:Arrr thats good do post up when your happy with it ,its something i would add for sure for a bench supply as that's where your so likely to find it fail ..Very good Steve !
Steve Anderson wrote:Harry Dalek wrote:Well we've all heard 'scratchy' volume controls, and that's where or dust dirt has got into the pot, and/or the wiper and/or track has simply worn out. One instant open circuit. Disastrous in a variable LM317/337 circuit, and many others...LM350 to name but one...
Steve A.
Klaas Robers wrote:But a bad contact of the wiper is much more likely.
Return to Construction Diaries
Users browsing this forum: No registered users and 0 guests