HI
i need to switch 1 amp at 12 volt, with isolation from the signal.
at around 20 times per second.
i was hoping to find an opto coupler or opto isolator that would do the job without an external output stage,preferably cheap, as i need 6 channels
i have done some searching, but the output current is 'never' stated in the specs.
if any members have any suggestions, it would be much appreciated.
tthank you
dougal

 

Well... Inasmuch as it seems you do not wish to follow a 'standard' isolator with a power semiconductor (why not?) -- you could use 'solid state relays' (many of which incorporate 'opto-isolated' inputs) -- Note, however, that you will require devices designed to switch DC (i.e. GTO output) -- else the input signal will 'lose control' following 'turn on'...

Best regards
HP

 

What you care about is cheap, that is less money, but the current more higher of components will be need more money and that it is not cheap.

I would suggest that you to using 6 photocouplers as PC817 and 6 stages of N mosfets.

How about the channels, is that 6 to 1 or 6 to 6 independent control?

 

hi
thank you for your repliies and prompt responses,
the way to go is of course an external driver stage, but with so many channels
i i would look to see if there were any alternatives.
i did look into ss relays but they costed out at around £40-£50,plus postage. hence my mention of price.
something that did come up was the 8 channel arduino relay boards, these are quite reasonable,but few if any in the uk, could work round 5 volt input i suppose.

i didnt mean to come across as cheapskate and lazy, but i suppose i am.

it was just a thought.

thanks again
dougal

 

The relay only suit for works under 10 times/sec.

 

i need to switch 1 amp at 12 volt, with isolation from the signal.
at around 20 times per second.
i was hoping to find an opto coupler or opto isolator that would do the job without an external output stage,preferably cheap, as i need 6 channels
i have done some searching, but the output current is 'never' stated in the specs.
if any members have any suggestions, it would be much appreciated.

IXYS make optically coupled MOSFET switches which can be used for DC. Not sure where you would obtain them in the UK, but here in the States they're available through Digi-Key:

http://www.digikey.com/product-search/en?pv434=72&pv434=152&pv434=73&pv434=75&pv434=76&pv434=78&pv434=79&pv434=117&pv434=80&pv434=116&pv434=121&pv434=120&FV=fff40010,fff80058,fffc00d4,1c0002,1c0003,1c0006&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

Perhaps one of those might do the job...

 

The LCA717 looks good enough. Not wild about the turn-on/off times, but they combine to less than 3% of the period (typ.).

ak

 

http://forum.allaboutcircuits.com/threads/opto-isolator.79984/
just spotted this, which will handle 1 amp but on the input.
the link to the chip is down.

 

HI
i need to switch 1 amp at 12 volt, with isolation from the signal.
at around 20 times per second.
i was hoping to find an opto coupler or opto isolator that would do the job without an external output stage,preferably cheap, as i need 6 channels
i have done some searching, but the output current is 'never' stated in the specs.
if any members have any suggestions, it would be much appreciated.
tthank you
dougal

There is an optocoupler with MOSFET output often used as the hookswitch function in modems.

It can handle about 230V, the current rating is higher than a typical opto but I can't remember exactly how high.

 

euraka/ish
might have found it, and a fiver for 5 on ebay.
im not well up on optos, could i ask someone to see if this would do the job,
only snag, theres always a snag . the supply rail needs to be 6v above output
voltage.als would have preferred through hole,
FOD3150S, OPTOCOUPLER, DIP-8, 1A, SMD

optoshttps://www.fairchildsemi.com/datasheets/FO/FOD3150.pdf

 

Maybe not. At 1 A current there is 6 V of drop across the output terminals. That 6 watts of internal power dissipation, enough to kill the part in seconds. Plus the datasheet notes that the 0.25 W power dissipation is not for continuous conditions. Sorry, keep looking.

ak

 

http://www.avagotech.com/pages/en/optocouplers_plastic/solid_state_relay_photo_mosfet/

Those look like they might be the ticket. Kind of expensive (for an 8 pin IC) but figure if you get the dual channel version, thats really a bargain for a two-pack of opto-isolated SSRs for 8USD.

Look for assr-1520-002e. Dual channel 1A 60V .5ohm rdsON in a dip8 package thru-hole