Hi mate,
Yes if anyone is interested, should I post the vero-board setup?
Al
Well a circuit diagram with component values is fine. A photo of hand-drawn diagram works.
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Hi mate,
Yes if anyone is interested, should I post the vero-board setup?
Al
Well thank you Diver.
It was good of you to bring up the turn on/off times of the components, but i think there is a much simpler explanation about the 5.5uH inductor. The minimum Ton time of the chip is spec'd at 19us, and with that much time and a 12v input voltage at the end of the Ton period the current in the inductor would have reached something like 40 amps, and we know that the transistor will never be able to handle that kind of current as it is limited to 1/2 amp. As a matter of fact, due to the input voltage and min Ton time the minimum inductance for this app would be about 456uH. Any lower than that and the current demand exceeds the internal transistors rating. Make sense to you?
Hello again,
Nice pics, thanks. So i guess you ended up using a 1.1mH inductor then? Do you happen to know its series DC resistance?
Hi mate,
Do you mean measured with the DMM?
I have an inductance and capacitance meter that I made some years ago and that particular inductor was the nearest I had measurement wise - measured 1.087mH and seems to be just the job.
Hi guys,
Mr Al, the res measures 1.3ohms but my DMM seems a bit high on small ohms, the dozens I have measured all seem to be about twice the marked value! So the inductor could well be 0.7ohms or anything in between.
Wish I could find a simple and accurate way of measuring the small ohms!
Al