On 1/7/2025 11:17 AM, Lukasz wrote:
This will be difficult . I can pull at most 4mA at 3.3V on the
control lines out of the uC board. That is not a lot of power....
I'm already at over half of that, so realistically ... I can't pull
more than 3mA with a bit of safety factor.
Then don't drive the base of the transistors directly. Use a
buffer/line driver between the controller and the transistors.
Alternatively, you may want to look at a voltage drive switching
device (FET) instead of the current controlled NPN transistor.
73,
... Joe, W4TV
On 1/7/2025 11:17 AM, Lukasz wrote:
On Tue, 7 Jan 2025, 15:42 Ron W4BIN, <ka4inm@gmail.com> wrote:
On 1/7/25 3:28 AM, Lukasz wrote:
I'm thinking about adding these capacitors as 100nF or 10nF (depending
which one will fit) smd parts right between the base and emitter the
pads.
Do you think that will work? If not, what would you do?
73,
Łukasz - SP4IT
The trick is to make the input to the problem relays to require POWER to
activate them. Feed a high current to those channels and drop the input
resistor divider down to the hundreds of Ωs.
Ron W4BIN
This will be difficult . I can pull at most 4mA at 3.3V on the control
lines out of the uC board. That is not a lot of power.... I'm already at
over half of that, so realistically ... I can't pull more than 3mA with a
bit of safety factor.
I think my problem may be a variation of the famous "pin 1" problem.
In my attempts to avoid ground loops I've not connected the shielding braid
on both ends to the case.
I just read you do that to avoid uV level hum on audio , not when a kilowat
of RF is flying past. So that's the first thing to change.
Then the coax that delivers +12V. The braid of that too is not terminated
on the chassis but goes inside. Despite having RF shorting cap to RF ground
right at case wall I think this may have to be replaced by a second coax.
Finally, if nothing helps at all I'll have to get rid of transistors and
replace them with transoptors. I wanted to avoid that, but it may be
required .
If anyone has one ideas please share.
73,
Łukasz - SP4IT (also SQ4KW)
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|