On Sep 11, 5:53*pm, John Smith wrote:
On 9/11/2010 3:04 PM, Geoffrey S. Mendelson wrote:

...
Has anyone run the radio with a 5 volt adaptor? Does it have a problem with
the 1/2 volt overage?

Thanks in advance,

Geoff.

- If you are really worried, perhaps better safe than sorry(?), drop a
- silicon diode in the line, in series with the supply, will drop the
- voltage ~0.68-0.75V.
-
- Regards,
- JS

JS - Why a Silicon Diode versus a Resistor
in the DC Output Line ? - iwtk ~ RHF

On Sep 11, 11:11*pm, RHF wrote:
On Sep 11, 5:53*pm, John Smith wrote: On 9/11/2010 3:04 PM, Geoffrey S. Mendelson wrote:

...
Has anyone run the radio with a 5 volt adaptor? Does it have a problem with
the 1/2 volt overage?

Thanks in advance,

Geoff.

- If you are really worried, perhaps better safe than sorry(?), drop a
- silicon diode in the line, in series with the supply, will drop the
- voltage ~0.68-0.75V.
-
- Regards,
- JS

JS - Why a Silicon Diode versus a Resistor
in the DC Output Line ? *- iwtk ~ RHF
*.

Because a silicon junction voltage drop is fairly stable 0.6-0.7
VDC,in general. A small light bulb (here we go,another incandescent!)
in series is fun to experiment with as well,since the current
consumption will be visible.

On Sep 12, 9:34*am, John Smith wrote:
On 9/12/2010 9:32 AM, RHF wrote:

...
Ah OK - I have always figured the required
Voltage Drop needed for the Radio at normal
Audio Listening Level and used a Resistor
-example- 12 VDC down-to 9 VDC -or 6 VDC.

Here you are using a Silicon Diode because it has
the specific ~0.6/0.8 Volt Drop for this application.
http://en.wikipedia.org/wiki/Diode

~ RHF
* .

Yes, if you want to drop the voltage further, just drop more silicon
diodes in series ...

Regards,
JS

HUMmmm the Cost of one Resistor
or the Cost of many Diodes . . .

Somewhere 'somewhen' long ago : I was told
taught to Divide my Dropping Resistor Value by
Two and use Two Resistors in the DC Supply line;
one in each Wire; so that the Battery would be
'isolated' and 'floating' ?

+12VDC [b]__/////__+Radio-__/////__[b] -12VDC

John Smith wrote:
On 9/12/2010 7:04 AM, dave wrote:


JS - Why a Silicon Diode versus a Resistor
in the DC Output Line ? - iwtk ~ RHF
.
The resistance needed varies with current draw?

To drop the voltage from 5 to 4.4-4V ... as I originally said ... the
voltage drop in silicone diodes is around 6.8, it can vary some due to
type, manufacturing process, etc.

Regards,
JS

I was taught six tenths for a Si diode rectifier, three tenths for Ge.

To keep the voltage constant, while current draw varies, requires a
variable resistance. I assume this happens inside the diode.

RHF schrieb:

On Sep 12, 9:34 am, John Smith wrote:

[...]
Yes, if you want to drop the voltage further, just drop more silicon
diodes in series ...

Regards,
JS

HUMmmm the Cost of one Resistor
or the Cost of many Diodes . . .

The voltage drop across a diode/diodes is more or less current
independend while the voltage drop across a resistor depends on the
current through that resistor. High volume - big current - big
voltage drop - low supply voltage; low volume - low current -
small voltage drop - high (maybe too high) supply voltage.

HTH

Reinhard

On 9/12/2010 10:39 AM, dave wrote:

...
I was taught six tenths for a Si diode rectifier, three tenths for Ge.

To keep the voltage constant, while current draw varies, requires a
variable resistance. I assume this happens inside the diode.

The old germanium I have measured tended to be close to 0.5v. The
schottky ~0.2 = ~0.4 unless under heavy loads ... and of course, there
are exemptions to the rule ...

Regards,
JS

John Smith wrote:
On 9/12/2010 10:39 AM, dave wrote:

...
I was taught six tenths for a Si diode rectifier, three tenths for Ge.

To keep the voltage constant, while current draw varies, requires a
variable resistance. I assume this happens inside the diode.

The old germanium I have measured tended to be close to 0.5v. The
schottky ~0.2 = ~0.4 unless under heavy loads ... and of course, there
are exemptions to the rule ...

Regards,
JS

It's been a while.