reversing polarity from using no switch

Hi, I need to be able to reverse a polarity using a momentary normally open push button. In open state I need the polarity one way, and in closed (momentary) state, I need it reversed. What is the best way of doing that? Thank you, Alan

Unless you use a DPST button, the momentary-on switch could energise a DPDT relay that reverses the polarity.

You can do it this way, either constant NEG and momentary POS or vice versa. You can also do it with a latching relay to give you either way constant but note latching relays will only give you up to 10 amps and you will need a SPCO momentary switch. Method 1:- rev_pol.bmp

Ah - I took it to mean polarity reversal as in a window winder, antennae, etc. Gotta love English...

Good point Peter.What did the OP mean? Now I'm confused. If we're talking motors antenna etc. DPCO centre off or SPCO centre off and two relays.

Well that's for the OP to clarify if it's an issue. I think your single-pole reversal is more likely to be correct, but it might be a dual-pole for motor reversing etc if other contacts do the on-off. Bit it's definitely a mom push button activation, hence SPDT or DPDT switch else SPST switch plus 1 SPDT or 1 DPDT else 2 SPDT for single and dual pole respectively.    Someone really should tel the Queen to clean up her English.    And if any Pomms complain that we don't use the Queen's English, please remind those ignoramuses that we use the King's English.

Actually if we are referencing English, you're Youngspark to me. Oz English is the English of the 1800s as American English is the English of the 1700s. Of course, English being the most evolved language with no rules whatsoever has moved on a heck of a lot since then with American, Yiddish, Irish, Scandanavian, German, African-American, Eastern European, Hispanic, all juggled together and via cultural dominance, Movies and TV influences all the other languages. SORRY!

How dare you call me young! I am officially now old. Do you know how long that has taken me? Now I enjoy watching young slammers & moshers and snoboarders etc respect me for my age (my mere abilities being unworthy of such respect.) But I disagree with "no rules" English... The spelling variations showed the word's origin (germanic, latin, frog etc). And there were good grammar rules so subjects were not confused. However in practice it is definitely a no-rules language. The spelling has changed (how stupid to spell phonetical with an F ) and I don't think anybody teaches or learns grammar. (I didn't until 2nd-year German when our disgusted teacher gave us a 2-week English grammar course.)    I am horrified that English is becoming the "international language". I think that alone will escalate the number of wars and disagreements. However in some ways its ambiguity and known penchant for misinterpretation may be good because it should force an extra level of tolerance.   And I have concluded that it is a better choice than Mandarin. But I'd prefer the exactness of something like German but without the genders etc. Maybe Esperanto?    At least English is an amalgam of several language roots and it - like most languages - is still evolving. We got our beloved "fair dinkum" (most likely) from Chinese; miljo and ombudsperson from the Scandies; even the Swedes now have "holiday" and "please". Maybe one day the French will get computers and data.    If only I could remember where "hijack" came from....

I don't know where it came from but it used to go to Cuba, nowadays it's weapons stolen from Oz navy vessels but what do you expect with an Oto Melara gun and an Israeli targeting system. I LOVED that Oz show, Sea Patrol was it called? Bugger off, it's nearly bedtime for this pom.

Ok, final hijack. I too laughed at the Darwin naval heist. I only saw it 'cos I was visiting my mother (I never watch the news etc). Of course I let out my usual catch-cry "Have they ruled out terrorism?" - that clarification being the start of so many news reports years ago. The joke being that we still live under the same (in-)doctrine of "Terror" and yet look around! (Of course (re-)action gets reaction and thence I can now be proven wrong.) But that's it - no more. I certainly don't want to be accused of any political hijacking! Jindalee's got Darwin anyhow...