Negative and positive voltage from one battery

Projects General Guidance
1

Hi Everyone,

I apologize if this is already a topic, but I could not find any info while searching the forum.

I am using the the sparkfun Muscle Driver V3 (MyoWare 2.0 Muscle Sensor - DEV-21265 - SparkFun Electronics)

The tutorial provided shows how to hook up this sensor using two 9V batteries. This works well, however my plan is to embed this sensor into a project using a LiPo battery,charger, servo motor and an arduino nano.

I can't seem to figure out how to supply negative AND positive voltage using a single battery. Is this possible using some type of hardware?

Thanks in advance for any help!

Matt

2

You can get "voltage doublers" which are simple circuits that charge and discharge a capacitor to do what you want. It's often used for adding to the positive voltage but it can easily be subtracted from the negative voltage too. It may also be known as a DC/DC converter.

For small power requirements (like a milliamp or so) a MAX232 chip has a neat voltage-doubler-and-inverter circuit on board. That's actually my choice these days to get a reference voltage or opamp supply below zero volts.

3

Thank you for the quick reply!

I found a DC/DC converter, but I don't think it does what I want: SparkFun DC/DC Converter Breakout - BOB-09370 - SparkFun Electronics

That MX232 chip you mentioned looks a little out of my league for figuring out myself, but I will give it a crack! Thanks again for your help.

Matt

4

The DC/DC converter you linked to has only one positive output.
You need a positive and negative supply (related to ground).

There are dual rail switching converters availabe.

But the MAX 232 seems an easier/better option for a light load.
Seems you only need four or five small caps to get this chip working.
Leo..

5

Thanks to the both of you for your help. Can you please comment on my schematic? I couldn't find the MAX 232, but I did find something similar the SIPEX SP3232 - datasheet

SP3232.JPG
SP3232.JPG1123×734 92.5 KB

6

So you are getting a bottle of champagne so you can use the cork for something.

Why not just google voltage mirror chip?

7

Can't seem to find a "voltage mirror chip" from anywhere that I can purchase. the SP3232 and MAX chips are readily available, and only cost $2.

Thanks for the help guys

8

Ok but be aware that the current draw you can take is in the order of a few mA.

Also that chip should be $0.50

9

OK thanks for the feedback, appreciated. Do you know where I can find a "voltage mirror" or happen to have a specific part number or part number in mind?

I believe I only need a few milliamps, but will need to check the spec sheet for the muscle sensor I am using.

Thanks for your help on this!

10

I use these.

2015-11-22_10-38-57.jpg

11

Awesome, thanks!