29-07-2015, 01:15 PM
I'm trying to think my way around a few problems and hope you may have some thoughts for a simple and clever solution to each. The problems relate to the LT supply for the curve plotter, which if you recall I'm proposing to derive from the AC mains supply.
To make operation slick I thought about employing fixed and trimmer resistors to produce 1.5, 2, 4, 6 and 6.3v heater supplies, selected via a rotary switch. The problem however is the range of filament current, which for 2v valves alone can vary from 0.07A to 0.2A. Other than reverting to a pot I don't know how to get around this. Any thoughts?
The next problem is filament protection from surge. Feeding the LT from the mains is all well and good, but is there a risk that a small power surge may blow the filament of a 1.5v valve? If so, what's the easiest solution?
I'm also concerned about valve performance. Throughout the duration of the tests I need a constant filament voltage. No problem using a DC cell, but I'm proposing to use a mains supply. How do I guarantee an even supply?
I really don't want to use batteries to supply the LT circuit.
Thanks.
Nick.
To make operation slick I thought about employing fixed and trimmer resistors to produce 1.5, 2, 4, 6 and 6.3v heater supplies, selected via a rotary switch. The problem however is the range of filament current, which for 2v valves alone can vary from 0.07A to 0.2A. Other than reverting to a pot I don't know how to get around this. Any thoughts?
The next problem is filament protection from surge. Feeding the LT from the mains is all well and good, but is there a risk that a small power surge may blow the filament of a 1.5v valve? If so, what's the easiest solution?
I'm also concerned about valve performance. Throughout the duration of the tests I need a constant filament voltage. No problem using a DC cell, but I'm proposing to use a mains supply. How do I guarantee an even supply?
I really don't want to use batteries to supply the LT circuit.
Thanks.
Nick.
