Re: [NYCR:Microcontrollers] Need Controllable Circuit that Varies Output Voltage

[Ted Hayes | Limina.Studio]

If you don't need the voltage to be super 100% flat, you could do a PWM output from the arduino, filter it, and amplify it with an op-amp.

PWM filtering: http://arduino-info.wikispaces.com/Analog-Output

Op-Amp: http://www.electronics-lab.com/blog/?p=1007

On Sep 17, 2012, at 3:26 PM, adamdb wrote:

I need to build a circuit, that can vary a voltage between 0 and 18 volts. This current will be connect to another device. The circuit in question must also be controllable via an Arduino Uno controller. I'm aware the the Uno has a max output of 5 volts, this is part of the problem. Any help, advice, links, or schematics would be greatly appreciated! Thanks.

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[Rob Graham]

You might try using the analog output of an Arduino to drive a power transistor like the Darlington 2N6284 (NPN).  It's going to depend on how much current you need to draw.

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From: adamdb <ada...@gmail.com>
To: nycresistormi...@googlegroups.com
Sent: Monday, September 17, 2012 2:26 PM
Subject: [NYCR:Microcontrollers] Need Controllable Circuit that Varies Output Voltage

[Guan Yang]

You can also use an LM317 and a digital potentiometer. For example this circuit:

http://www.electronics-lab.com/articles/LM317/

Here's a cheap 5K potentiometer that's discontinued but still in stock at Digi-Key:

http://www.digikey.com/product-detail/en/MCP4132-502E%2FP/MCP4132-502E%2FP-ND/1874332

Here's a larger one with 257 steps:

http://www.digikey.com/product-detail/en/MCP4251-502E%2FP/MCP4251-502E%2FP-ND/1635677

If you get that one, around 9V, you would get about 0.11V precision.

On Monday, September 17, 2012 at 16:21 , Rob Graham wrote:

> You might try using the analog output of an Arduino to drive a power transistor like the Darlington 2N6284 (NPN). It's going to depend on how much current you need to draw.
>

> From: adamdb <ada...@gmail.com (mailto:ada...@gmail.com)>
> To: nycresistormi...@googlegroups.com (mailto:nycresistormi...@googlegroups.com)
> Sent: Monday, September 17, 2012 2:26 PM
> Subject: [NYCR:Microcontrollers] Need Controllable Circuit that Varies Output Voltage
>
> I need to build a circuit, that can vary a voltage between 0 and 18 volts. This current will be connect to another device. The circuit in question must also be controllable via an Arduino Uno controller. I'm aware the the Uno has a max output of 5 volts, this is part of the problem. Any help, advice, links, or schematics would be greatly appreciated! Thanks. --
> You received this message because you are subscribed to the Google Groups "NYCResistor:Microcontrollers" group.
> To view this discussion on the web visit https://groups.google.com/d/msg/nycresistormicrocontrollers/-/T3idQzLpce0J.

> To post to this group, send email to nycresistormi...@googlegroups.com (mailto:nycresistormi...@googlegroups.com).
> To unsubscribe from this group, send email to nycresistormicrocon...@googlegroups.com (mailto:nycresistormicrocon...@googlegroups.com).

> For more options, visit this group at http://groups.google.com/group/nycresistormicrocontrollers?hl=en.
>
>

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[Benjamin]

This depends entirely on the rate at which you need it to change. As you mention Arduino, we can assume a fairly slow rate of change. The least complex design involves a low-side transistor connected to pwm through a 270ohm resistor, Then feed the result back to Arduino with a voltage divider into an ADC. monitor the ADC for the voltage desired adjusting the PWM as needed; depending on the load, you may want to add a capacitor across the output to smooth the voltage.

Chances are however that you don't actually want 0-18 volts, if you're driving a motor, you just need PWM to adjust speed, This is how we adjust current in a microcontroller world. Real current control is big, expensive, and hot (pick two).

 

 

[adamdb]

Thanks for the reply Benjamin. This will ultimately be used to control the speed of cars on a slot car race track. The track takes from 0 - 18v.

[joseph legros]

Anyone here had any favorable dealings with having flex PCB's made? What was the average turn-around time?

Thanks,
Jhosef