# Programable polarity reversal circuit

#### Mateusz Rowicki

Joined Apr 7, 2016
4
Hi so I am a Civil engineering student with very little knowledge in circuits so I apologize if this question is redundant or common.

I need to make a circuit that applies voltage but will reverse polarity with a given time interval and I cannot seem to find a solution for this.
I am applying about 10V through DC and need to have like a programmable or modular circuit where we can change the timing of the polarity reversal, say 1min for 10V and then 1min for negative 10V and back to 1 minute of positive 10V. The timing has to be long (so no AC), this is what my trouble is in.

I believe the device link below is what we need but it is way to expensive for me to buy.
http://www.ebay.com/itm/NEW-DIGITAL...EVERSING-RELAY-CONTACTOR-SWITCH-/190585630987

So can someone possibly give me a possible circuit with details to conduct this polarity reversal for longer intervals. Also, if you know of any cheaper devices that can do this, that would be also ideal.

If you need more details let me know.

Joined Jul 18, 2013
28,829
A 555 astable operations circuit should do it, there are several sources on the web for these 555 based circuits.
Max.

#### dl324

Joined Mar 30, 2015
17,142
Are you just trying to reverse voltage polarity? What voltages and currents are involved?

I'm thing something along the lines of a DPDT relay. A diagram would help.

#### mcgyvr

Joined Oct 15, 2009
5,394
It also helps to fully describe your needs instead (or along with) of what you think you need to do as you could be going down the wrong road and getting answers to your question but not really solving your problem..

One might assume you are trying to control a motor in 2 directions which may be done with an h-bridge which can be made with mosfets/relays/transistors,etc.. based on the needs..

#### Mateusz Rowicki

Joined Apr 7, 2016
4
It also helps to fully describe your needs instead (or along with) of what you think you need to do as you could be going down the wrong road and getting answers to your question but not really solving your problem..

One might assume you are trying to control a motor in 2 directions which may be done with an h-bridge which can be made with mosfets/relays/transistors,etc.. based on the needs..

I am trying to apply a current through a soil sample in order to consolidate it faster using Electro-Osmosis. Polarity Reversal should theortically speed the process of consolidation. Hence I need a circuit that will allow me to apply 10V but alternate polarity every minute for example

#### Mateusz Rowicki

Joined Apr 7, 2016
4
Are you just trying to reverse voltage polarity? What voltages and currents are involved?

I'm thing something along the lines of a DPDT relay. A diagram would help.

See reply to other poster. My sample has an anode and cathode at each end of the soil sample in a tube. I basically just need a circuit that reverse the polarity past the power supply

#### Marcus2012

Joined Feb 22, 2015
425
Hi
Sorry do you actually need -10V, or do you just need the direction of current flow between the two points to reverse (swapping anode and cathode)?

The later can be achieved as Maxheadroom suggests with a 555 astable timer operating a DPDT as dl324 suggested.

If it is the former however, it is a little more difficult. You could use a centre-tapped secondary to produce a -10V potential from mains supply but this is expensive, or alternatively use a DC-DC converter to get -12V from 12V. These do not usually have very large current capabilities however the LTC3863 states a 1A-1.7A in example diagrams. It is the subject of this article the manufacturer published. I do not know the construction costs of these circuits and have never had the need to construct one but I do not imagine it is easy or cheap.

Inverting DC/DC Controller Converts a Positive Input to a Negative Output with a Single Inductor

That would only be for the -10V supply, to switch between the two you'd still need to implement the timer, transistors and possibly a flip-flop to clean up the transition.

Last edited:

#### Mateusz Rowicki

Joined Apr 7, 2016
4
B
Hi
Sorry do you actually need -10V, or do you just need the direction of current flow between the to points to reverse (swapping anode and cathode)?

The later can be achieved as Maxheadroom suggests with a 555 astable timer operating a DPDT as dl324 suggested.

If it is the former however, it is a little more difficult. You could use a centre-tapped secondary to produce a -10V potential from mains supply but this is expensive, or alternatively use a DC-DC converter to get -12V from 12V. These do not usually have very large current capabilities however the LTC3863 states a 1A-1.7A in example diagrams. It is the subject of this article the manufacturer published. I do not know the construction costs of these circuits and have never had the need to construct one but I do not imagine it is easy or cheap.

Inverting DC/DC Controller Converts a Positive Input to a Negative Output with a Single Inductor

That would only be for the -10V supply, to switch between the two you'd still need to implement the timer, transistors and possibly a flip-flop to clean up the transition.

Basically, I need the voltage the is being applied to alternate form positive to negative every minute. I have a power supply which has a DC option and I can change the frequency but the slowest alternation i can get is about every 3 seconds which is to fast for what I need. However thank you for the information thus far, I will continue reading into this

#### Marcus2012

Joined Feb 22, 2015
425
This would probably be the easiest way if you can find an inexpensive 10V centre tapped transformer (and use 7810s instead) and then you could just use the + rail to power your switching circuitry.

#### AnalogKid

Joined Aug 1, 2013
11,202
Do you already have the 10 V power source? If yes, then this can be done with some very low cost modules on ebay.

http://www.ebay.com/itm/SMALL-DC-MO...102458?hash=item33b374b5ba:g:N-sAAOSwYlJW505q
or
http://www.ebay.com/itm/DPDT-Signal...hash=item5d32d78610:m:mQZwTF319Zmxn-pF8rL0jww

controlled by
http://www.ebay.com/itm/DC-12V-Mult...611343?hash=item3abf3df30f:g:dDkAAOSwAuNW4qD9
or
http://www.ebay.com/itm/DC-12V-Infi...399364?hash=item2a5c31e1c4:g:~8wAAOSwZVhWTG~d

Do you have an estimate of the peak current the power source needs to supply to the soil sample?

ak

#### dannyf

Joined Sep 13, 2015
2,197
a programmable or modular circuit where we can change the timing of the polarity reversal,
A dpdt / relays would work.

A fancier version would require a H-bridge.