M
Michael Robinson
- Jan 1, 1970
- 0
Hello fellas
I breadboarded the circuit in this magazine article:
http://electronicdesign.com/article/power/single-solar-cell-trickle-charges-3-to-16-v-batter.aspx
and eventuallly figured out how it works.
In the text, the author never zeros in on what actually makes the circuit
switch.
All that's really happening is that the draw from the inductor sucks charge
out of C2, turning off Q2 which flips the inverter U1a, turning Q4 off, then
C2 charges up, the mosfet turns back on etc. I found this out because I
tried to drive the circuit from a low impedance power supply set to .65
volts and it didn't work, but with a little resistance in series with the
..65 volts it ran. I also found out that C4 has very little effect; I simply
yanked it out of the breadboard. The circuit kept running, and the
frequency changed less than 10%.
The circuit below is a lot simpler than what's in the article and does
exactly the same thing (view in monospaced font):
,------+------------------------------------------,
| | |
| 1R )
| | ) 160uH
| --- solar )
| - 0.65v
| ---
,--------+--------------------------|------------------+------,
| - | | | BAT54 |
|
| | | ,-------, +-->|--+--2R--+----+
|
| | +---|1 14 \ 1N4148 | | | |
|
| gnd | | \ |--' | | |
|
| 1M | 3 )o---+-->|----+--|| 100uF |
---
| | | / | | |--, | | |
batt -
| +---|2 7 / | < |IRF530| |
---
| | '-------' '------| | | 100uF
-
| / | \ | | | |
|
+---100k-+--| PN2222 | CD4093 2N3906 | | | | |
|
| | > | | | | | zener
|
| | | | | | | | |
|
10uF 1M | | | | | | |
|
| | | | | | | | |
|
'--------+----+--------+-------------------+------+------+------+----+------'
|
gnd
What's funny is that I'm in a college EE class where the professor assigned
us this circuit to build in the lab and do a report on. He posted the
diagram but not where it came from. The professor repeated the explanation
from the electronics design article. Everybody went in the lab, built the
circuit and did reports on it, including me. It was actually our final
project of the semester, and each lab group had to work up a power point
presentation and give it in front of the class. While we were in the lab
building the circuit, I figured out that C4 was pretty much pointless, the
timing was done at C2 and said so during our presentation, but it was only
last nigh that I twigged to the fact that three of the gates and a bunch of
passives are useless as well.
So this morning I got on the computer and was able to find where our prof
got that circuit. I think I also located the author. There's a George
Woolcott living in Harrodsburg KY, near Lexington, which is where the
author's employer Lexmark has its headquarters. I'm considering contacting
him and telling him our college class built his circuit as an assignment and
ask if he would like to comment on it.
But the semester is ending in just a few days. I don't have hiis email and
would have to call him on the land-line number I found. I suppose I should
just talk to the professor instead.
I breadboarded the circuit in this magazine article:
http://electronicdesign.com/article/power/single-solar-cell-trickle-charges-3-to-16-v-batter.aspx
and eventuallly figured out how it works.
In the text, the author never zeros in on what actually makes the circuit
switch.
All that's really happening is that the draw from the inductor sucks charge
out of C2, turning off Q2 which flips the inverter U1a, turning Q4 off, then
C2 charges up, the mosfet turns back on etc. I found this out because I
tried to drive the circuit from a low impedance power supply set to .65
volts and it didn't work, but with a little resistance in series with the
..65 volts it ran. I also found out that C4 has very little effect; I simply
yanked it out of the breadboard. The circuit kept running, and the
frequency changed less than 10%.
The circuit below is a lot simpler than what's in the article and does
exactly the same thing (view in monospaced font):
,------+------------------------------------------,
| | |
| 1R )
| | ) 160uH
| --- solar )
| - 0.65v
| ---
,--------+--------------------------|------------------+------,
| - | | | BAT54 |
|
| | | ,-------, +-->|--+--2R--+----+
|
| | +---|1 14 \ 1N4148 | | | |
|
| gnd | | \ |--' | | |
|
| 1M | 3 )o---+-->|----+--|| 100uF |
---
| | | / | | |--, | | |
batt -
| +---|2 7 / | < |IRF530| |
---
| | '-------' '------| | | 100uF
-
| / | \ | | | |
|
+---100k-+--| PN2222 | CD4093 2N3906 | | | | |
|
| | > | | | | | zener
|
| | | | | | | | |
|
10uF 1M | | | | | | |
|
| | | | | | | | |
|
'--------+----+--------+-------------------+------+------+------+----+------'
|
gnd
What's funny is that I'm in a college EE class where the professor assigned
us this circuit to build in the lab and do a report on. He posted the
diagram but not where it came from. The professor repeated the explanation
from the electronics design article. Everybody went in the lab, built the
circuit and did reports on it, including me. It was actually our final
project of the semester, and each lab group had to work up a power point
presentation and give it in front of the class. While we were in the lab
building the circuit, I figured out that C4 was pretty much pointless, the
timing was done at C2 and said so during our presentation, but it was only
last nigh that I twigged to the fact that three of the gates and a bunch of
passives are useless as well.
So this morning I got on the computer and was able to find where our prof
got that circuit. I think I also located the author. There's a George
Woolcott living in Harrodsburg KY, near Lexington, which is where the
author's employer Lexmark has its headquarters. I'm considering contacting
him and telling him our college class built his circuit as an assignment and
ask if he would like to comment on it.
But the semester is ending in just a few days. I don't have hiis email and
would have to call him on the land-line number I found. I suppose I should
just talk to the professor instead.
