See last months chain re vibrators and your comments relative to the inverter schematic again.
What do you calculate the cap should be for 115cps inverter operation? What is the formula involved for calculating this and where would I find such a thing?
What would have to change in the schematic if the input voltage were 6 volts instead of 12 ?
Thanks!
Glenn
I'll start this off until John has a chance as I noticed you posted the question last month. The inverter John pointed out was operating at 60 cycles. He cut capacitor values in half which would double frequency.
You can not determine exact frequency as these capacitors usually have +80 -20% tolerance. To get an exact 115 cycles you need to experiment with values while using a scope or frequency counter.
To change from 12 to 6 volts a different transformer is needed. Base drive for transistors should also be increased. I am not looking at the schematic but base resistor values should be reduced.
Build up the circuit John pointed out. Check frequency on the bench before using it in a radio. Loading will also have an effect on frequency. Frequency isn't critical but it's nice to be close.
John will probably add more..
Norm
:
:John
:
:See last months chain re vibrators and your comments relative to the inverter schematic again.
:
:What do you calculate the cap should be for 115cps inverter operation? What is the formula involved for calculating this and where would I find such a thing?
:
:What would have to change in the schematic if the input voltage were 6 volts instead of 12 ?
:
:Thanks!
:
:Glenn
Glenn
:
::
::John
::
::See last months chain re vibrators and your comments relative to the inverter schematic again.
::
::What do you calculate the cap should be for 115cps inverter operation? What is the formula involved for calculating this and where would I find such a thing?
::
::What would have to change in the schematic if the input voltage were 6 volts instead of 12 ?
::
::Thanks!
::
::Glenn
Capacitor along with a resistor make a time constant. By cutting the capacitor value in half so is the time.
Here is a standard that I use. Capacitor of 100 mfd & resistor of 10K give one second delay. If the capacitor is reduced to 50 mfd the time delay would be .5 seconds.
An actual circuit may not operate on an exact time constant. Depends on turn on point of the transistor. In any case cutting capacity in half shortens time to 1/2 and doubles frequency.
Norm
::Hi Glenn
::
:: I'll start this off until John has a chance as I noticed you posted the question last month. The inverter John pointed out was operating at 60 cycles. He cut capacitor values in half which would double frequency.
::
:: You can not determine exact frequency as these capacitors usually have +80 -20% tolerance. To get an exact 115 cycles you need to experiment with values while using a scope or frequency counter.
::
:: To change from 12 to 6 volts a different transformer is needed. Base drive for transistors should also be increased. I am not looking at the schematic but base resistor values should be reduced.
::
:: Build up the circuit John pointed out. Check frequency on the bench before using it in a radio. Loading will also have an effect on frequency. Frequency isn't critical but it's nice to be close.
::
:: John will probably add more..
::
::Norm
::
::Thanks Norm - hope John has some thoughts also. How do you guys know that cutting the capacity in half would double the speed? I still would like to know if there is a mathematical formula someplace that explains how to compute such. Would this data be given in a transistor manual? John said the original capacitance stated was "calculated as correct" for 60 hz. I would sure like to know what the formula is for such a calculation. Well I am repeating myself now - thanks again for the tip on the IF cans.
:
:Glenn
::
:::
:::John
:::
:::See last months chain re vibrators and your comments relative to the inverter schematic again.
:::
:::What do you calculate the cap should be for 115cps inverter operation? What is the formula involved for calculating this and where would I find such a thing?
:::
:::What would have to change in the schematic if the input voltage were 6 volts instead of 12 ?
:::
:::Thanks!
:::
:::Glenn
At any rate, Norm covered it well without diving into the math. If Glenn wishes to look into the math a lot more deeply, the "ARRL Radio Amaturer's Handbook" (any edition) covers the basic math concepts for capacitor charge time, RC charge time (Resistor/Capacitor), LC charge time, resonance, etc.
At it's simplest math (other variables are held constant, so they can be cancelled out the equation) for a given charge time "T" (for a 1/2 cycle at the resonant frequency) in an "RC" circuit, reducing the capacitance while maintaining the resistance the same results in "1/2T". Or effectively increases the frequency of resonance by two. I may have oversimplified this too much, but there is math, it is essentially the formula for determining resonance.
One option for running a 6 volt radio off of 12 volts is to put about 1.7 Ohms (20 Watts) in series with the 12 volt supply. Then swapping transformers is not needed.
For the exact series resistance, find out what your actual current draw is, and use Ohm's law to calculate the correct value. Most 6 volt automotive systems ran between 6.3 volts and 7.5 volts, so you have a little room for cushion if your resistance is close and not exact.
:Hi Glenn
:
: Capacitor along with a resistor make a time constant. By cutting the capacitor value in half so is the time.
:
: Here is a standard that I use. Capacitor of 100 mfd & resistor of 10K give one second delay. If the capacitor is reduced to 50 mfd the time delay would be .5 seconds.
:
: An actual circuit may not operate on an exact time constant. Depends on turn on point of the transistor. In any case cutting capacity in half shortens time to 1/2 and doubles frequency.
:
:Norm
:
:
:
:::Hi Glenn
:::
::: I'll start this off until John has a chance as I noticed you posted the question last month. The inverter John pointed out was operating at 60 cycles. He cut capacitor values in half which would double frequency.
:::
::: You can not determine exact frequency as these capacitors usually have +80 -20% tolerance. To get an exact 115 cycles you need to experiment with values while using a scope or frequency counter.
:::
::: To change from 12 to 6 volts a different transformer is needed. Base drive for transistors should also be increased. I am not looking at the schematic but base resistor values should be reduced.
:::
::: Build up the circuit John pointed out. Check frequency on the bench before using it in a radio. Loading will also have an effect on frequency. Frequency isn't critical but it's nice to be close.
:::
::: John will probably add more..
:::
:::Norm
:::
:::Thanks Norm - hope John has some thoughts also. How do you guys know that cutting the capacity in half would double the speed? I still would like to know if there is a mathematical formula someplace that explains how to compute such. Would this data be given in a transistor manual? John said the original capacitance stated was "calculated as correct" for 60 hz. I would sure like to know what the formula is for such a calculation. Well I am repeating myself now - thanks again for the tip on the IF cans.
::
::Glenn
:::
::::
::::John
::::
::::See last months chain re vibrators and your comments relative to the inverter schematic again.
::::
::::What do you calculate the cap should be for 115cps inverter operation? What is the formula involved for calculating this and where would I find such a thing?
::::
::::What would have to change in the schematic if the input voltage were 6 volts instead of 12 ?
::::
::::Thanks!
::::
::::Glenn