I have diagram I used from Reef Angel showing how to take a 12v input and turn it into 10v so I am able to use the arduino for a 10v PWM Led light controller. Anyways I made it based on the schematics. Had a little trouble at first as I didnt realize I need a ground from the arduino to tie into it. Now, to test 10v PWM I used the standard Fade sketch example and I can go all the way to -0- however it will only go up to 8 1/2 ish volts through the PWM cycle. I even tried slowing it down to 1 sec per change to be able to read the numbers better. I am just seeing if that high number for me is normal or should I be topping out at 10v. before I added the ground to the Arduino it would go a little above 10 but did not go lower than 8 1/2 ish. Wierd. Heres the link to the forum as I cannot download the picture. Reef Angel Controller • View topic - PWM booster
Also it seems I can run 2 seperate channels off of this when using the LM35 depending on the specs of the driver I am trying to control, would that be a correct guess??
Thanks to whoever helps I appreciate it.
I think the output of that opamp cannot get all the way up to V+ (it can in theory but not in practice.)
If you need 10V out of it then you'll need a approx. 12V supply.
Refer to :"Output Voltage - High Limit" in the tables
http://www.onsemi.com/pub_link/Collateral/LM358-D.PDF
12V is not called out, but you can see that for 5V and 30V that the top end is less than supply.
Thats the thing. I am using a 12v supply. Any ideas?
An op amp is also limited to the ammount of current it can supply, which is not very much. That is why younare limited to the number of drives you can connect. You need to increase this current capability with a transistor. In fact just use a transistor forget about the op-amp.
GrundelGravy:
Thats the thing. I am using a 12v supply. Any ideas?
Sure about the 12V ("dead certain")?
What are the outputs when disconnected from any load?
Its at 12 at the input actually slightly above it drops at the second resistor. Do you have a schematic that uses what ypu are saying. Dropping the op amp all together? This all somewhat new to me. Heck I was pretty proud just making it drop from 12v.
That was fast. Lol. What is that to the right of the 4.7k resistor. Also could I just use a 12v in vs 10v by changing out the 1k resistor?
Nevermind. is that a PNP transistor or NPN? Is there a particular size??
is that a PNP transistor or NPN
It is the symbol for an NPN I used therefore it would be reasonable to suspect it is a NPN.
Also could I just use a 12v in vs 10v by changing out the 1k resistor?
No matter what value resistor you choose it will output the voltage on the other end of the resistor.
If you want to use 12V the get a 10V regulator in front of the supply.
Nice answer. I have 12v coming in through the 1k resistor connect to the collector pin of the LM317(left pin). The output of the Arduino to the 4.7k resistor connected to the base pin(middle pin). The Emitter pin connects to GND as well as 12V adapter and Arduino GND's. Where is the 10V coming out of, which pin? Am I headed in the right direction??
The LM317 is not a transistor, it has no collector pin. It has an input, output and adjust pin. You put a 220R resistor from the out pin to the adjust pin. A 1K6 resistor from the adjust pin to ground. And a 0.1 cap from the input to ground and another from output to ground. You then take the output to the top of the 1K resistor iin the circuit I last gave you.
Note you only need one of these LM317 to drive a whole bunch of transistors.
I was wondering, Mike, whether the LM317 is the 12V source or something and the rest of it is "failure to communicate."
Well the LM317 is a variable voltage regulator and that is being used to drop 12V down to 10V, as I see it.
Just so I am on the right page. Where is the arduino's pwm going into the adjuster? Not input right? and the out put would come from the 1k resister from the output, correct?
As labled the arduino is attached to the base resistor of the transistor on the left.
Don't forget all the grounds must be connected together.