Search found 24 matches

by simf14
Thu Oct 04, 2007 7:15 am
Forum: General Discussion
Topic: Ohms Law application
Replies: 7
Views: 1762

will try a LM338K...5A with 7A peak...should be plenty...thanks MrAl!!!

cp out
by simf14
Wed Oct 03, 2007 7:22 am
Forum: General Discussion
Topic: Ohms Law application
Replies: 7
Views: 1762

Thank you guys, your right. I am going to build something with a LM330 power transitor.

Thanks again.
by simf14
Tue Oct 02, 2007 7:28 am
Forum: General Discussion
Topic: Ohms Law application
Replies: 7
Views: 1762

Hello Mr. Al!!! I am trying to decrease the output of a 120V AC/DC 3-12V variable output, 4A switching power supply down to around a 1 V-8V range. :grin: I tried attaching a 10 Ohm, 10W ceramic block resistor but this did not drop the voltage at all when measured by an Ohm Meter. Could my resistor b...
by simf14
Mon Oct 01, 2007 8:21 pm
Forum: General Discussion
Topic: Ohms Law application
Replies: 7
Views: 1762

Ohms Law application

Kind Sirs:

I would like to drop 3.3V, 3As down to 1V, 3A with a ceramic resistor if possible. Could someone show me the correct way to figure out the proper value of the resistor and its watts?

Thank you.
by simf14
Tue Aug 21, 2007 7:28 am
Forum: General Discussion
Topic: Voltage Controlled Voltage Amplifier/ Mr. Al
Replies: 29
Views: 5163

Could anyone suggest a very nice TO-3 heatsink that they approve of?
by simf14
Mon Aug 20, 2007 10:44 pm
Forum: General Discussion
Topic: Voltage Controlled Voltage Amplifier/ Mr. Al
Replies: 29
Views: 5163

Yeah Chris talking op temps of 95F to 140F. (Nice pooch.) Man I hope Mr. Al doesn't kill me. I have been assuming you guys have been talking F instead of C the whole time. Looking at Mr. Al's theoretical calculations now everything is actually running cooler than expected!!!! (emoticon for extreme e...
by simf14
Mon Aug 20, 2007 10:41 pm
Forum: General Discussion
Topic: Voltage Controlled Voltage Amplifier/ Mr. Al
Replies: 29
Views: 5163

Wow what a great community there is on this board-everyone truly is interested in a lowly beginner and so helpful. This is a little embarrassing but I noted that with a moderate airflow over the heatsinks they now stay below 95 degree F on the voltage controlled voltage amplifier (12V, -12V supply, ...
by simf14
Mon Aug 20, 2007 8:29 pm
Forum: General Discussion
Topic: Voltage Controlled Voltage Amplifier/ Mr. Al
Replies: 29
Views: 5163

I actually built one protoboard with a breadboard and then a second hardwired board. Tested both under actual conditions but unfortunately not long enough! Anyhow did the heat test tonight. Added a 3 inch heatsink, the largest I could find, attached it to the LM338 with heatsink compound and solid b...
by simf14
Mon Aug 20, 2007 1:37 pm
Forum: General Discussion
Topic: Voltage Controlled Voltage Amplifier/ Mr. Al
Replies: 29
Views: 5163

thanks Philba and Robert...will pickup a larger heat sink today and then take some readings- very informative. I am committed to this approch now but I know PWM is used freqently too.
by simf14
Mon Aug 20, 2007 7:06 am
Forum: General Discussion
Topic: Voltage Controlled Voltage Amplifier/ Mr. Al
Replies: 29
Views: 5163

Dear Mr. Al I am using a smaller heat sink for the 338K TO-3 that is diamond shape with slotted vertical fins and about 2in long 1in wide and 2 in high so it would not take too much space on the board and it was the most common one I found. I will pick up a digital thermometer tonight but I know it ...
by simf14
Mon Aug 20, 2007 4:10 am
Forum: General Discussion
Topic: Voltage Controlled Voltage Amplifier/ Mr. Al
Replies: 29
Views: 5163

A little note is if I change the circuit input voltage from 12V to 9V, the 338 doesn't even get warm...Probably takes most of the work away from the 338(?)
by simf14
Sun Aug 19, 2007 7:23 pm
Forum: General Discussion
Topic: Voltage Controlled Voltage Amplifier/ Mr. Al
Replies: 29
Views: 5163

Hi Chris- nice big one, this one really does boil...it is so far below it's rated cap (-3X) I can't believe it should get that hot, I haven't be daring enough to see if it hits thermal shutdown but I believe it would.
by simf14
Sun Aug 19, 2007 5:26 pm
Forum: General Discussion
Topic: Voltage Controlled Voltage Amplifier/ Mr. Al
Replies: 29
Views: 5163

Voltage Controlled Voltage Amplifier/ Mr. Al

Mr. Al you recently spent an tremendous effort helping me get this circuit working exceptionally. I have a problem now in actual usage which maybe you could offer a few suggestions. The circuit powers a 12V, 30W, max 3A hydraulic solenoid. The 338K and large heatsink gets very "hot" (too hot to touc...
by simf14
Fri Aug 10, 2007 5:45 am
Forum: General Discussion
Topic: touch screen
Replies: 1
Views: 788

touch screen

Has anyone ever played with the idea of DIY touch screen circuits.? Possibly infrared LED? I have 5, 17" monitors I would like to do so to without spending a lot of $$$ on.

Thanks you!
by simf14
Fri Aug 03, 2007 9:47 am
Forum: General Discussion
Topic: Isolator/Amplifier
Replies: 29
Views: 4034

awesome

Perfect Thank you so much Al. Really sweet. The R3 gets a little warm, would it be as easy as just going to a 1.0 or 2.0 watt?? In case I want change the max output from 0-8V to 0-6V which resistor(s) would that be? You have a friend for life in Orange County Ca. / [email protected].net Free Root C...