DPDT latching relays 20 cents each
localroger
Posts: 3,451
http://www.goldmine-elec-products.com/prodinfo.asp?number=G19618
These are dual coil, so you don't need polarity reversal to switch them.
Of course you have to buy 500 for USD$100 but I am seriously tempted to drop a Benjamin in case I ever get the energy to do a relay computer. DigiKey lists this part at > USD$1600 for the same 500 count reel.
These are dual coil, so you don't need polarity reversal to switch them.
Of course you have to buy 500 for USD$100 but I am seriously tempted to drop a Benjamin in case I ever get the energy to do a relay computer. DigiKey lists this part at > USD$1600 for the same 500 count reel.
Comments
I don't think reverse polarity was ever needed for single inputs latching relays, you just pulse with change state. The issue is that you can loose track of the state without having some sort of monitoring in place.
These are simpler.. one input pulses to one position, the other input pulse to the other.
I bought a 100 pc box of almost similar ones quite long time ago, still kickin'
http://web.cecs.pdx.edu/~harry/Relay/
It's quite possible that memory banks can be optimised with these relays...
I'd order a 500pack myself, but they don't ship to Norway...
(well, maybe 512 would be a better number?)
EDIT:
Gosh, doing a "5V Relay 100" search on The Bay of E sure brings up a few interesting options.
http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.TR11.TRC1.A0.X5V+relay+100&_nkw=5V+relay+100&_sacat=0&_from=R40
But the dual coil latchers are a specialty item. You hardly ever see them cheap at all, much less this cheap, and they are much more powerful than normal relays because they are stateful and the separated coils give you a great many control options. That's what pushed me over the edge; I may never see a deal like this again. I've been playing with circuits and it is just stupidly easy to build counters and sequencers with these things compared to normal relays.
Harry Porter's relays were 4PDT but I think the latching goes a long way toward making up for just being DPDT. I may not build a computer with them but a really fancy clock would be dead simple circuitwise.
(Since I can't buy them myself. )
If you can effect the purchase but not the shipping I would not be averse to accepting them drop-shipped to me and forwarding a whole roll to you for whatever the USPS charges. Seems like that would be a better deal if you really want a lot of them. Otherwise when they arrive I'll see how many I can get in an envelope.
(NB the sale expires on the 19th.)
Or am I missing something?
I get the inner dimensions of the box I listed to be 219 x 136 x 41 mm?
And assuming the relays are stacked tightly the same way ( 15 x 7.4 x 8.4 mm , rounded up to 16 x 8 x 9 mm) I end up with 13 x 17 x 4 = 884 relays should fit in the box, with some slack for padding?
how much do you want for 500 relays?
($100 + shipping + your cut + shipping to Norway. PM me with an addy and I'll PayPal you the money )
They're about 2grams each, so that should make an even Kg, or about 2.2lbs, well within the weight limit, too.
Mouser seems to have these at slightly over $4 for singles, and doesn't drop below $3 until about the 100 mark.
Do they keep their state if they lose power?
They do hold state on power loss, that's the "latching" part. It's what makes them really neat to work with. Counters and shift registers are actually easier to implement than simple gates and they're non-volatile.
Maybe if you cut the tape in lengths that fit the inside of the box, then lay them beside each other with every other upside down?
That should pack them pretty tightly.
(I don't know the gap between the relays on the tape.)
http://www.panasonic-electric-works.se/catalogues/downloads/relays/ds_61022_en_tx.pdf
Still very tempting to make an order and sell what I don't need.
...and verified experimentally, they switch at 3v3 but not from an unbuffered Prop pin, which can only push about 2.6 volts to the 125 ohm coils.
C.W.
The proper way to transmit a logic signal for these relays requires two wires, one which is powered for "0" and one which is powered for "1." This means all logic signals can also be tri-stated by not powering either pin, and both pins powered is undefined because that usually means powering both coils in the latching relay. "Powered" means cleanly powered by pure DC through nothing but contacts. If passives are used to mix signals, they must be buffered by a relay to create a new compliant signal. It's surprisingly unhelpful to wire contacts in series and these 2PDT parts seem about as capable as 4PDT normal relays, although sometime with some help from a few diodes or resistors.
Using this method, it is possible to build:
-- Counters and shift registers with 2 relays per bit and one each positive and one clean free output
-- Using 2 resistors of about the same resistance as the coil, coil level AND by presenting two clean signals through resistors. Coils will not switch at 2.5V but will at 3.3.
-- Since separate OR (diodes/short) or AND can be applied to set and reset, any 2 input to 1 output logic function with 1 relay and at most 4 passives, and 2 independent outputs.
-- 2 to 4 decoder with 4 relays and 8 each resistors and diodes. (AND to output on, OR to output off, 4 combinations each.) These can be cascaded.
-- Square wave relaxation oscillator with one relay and some R/C passives.
If anybody is interested tomorrow I'll do some screencaps from ExpressPCB. I also need to mic out the pins once they're straightened (the rows are closer than a normal DIP) and create a properly pinned schematic and physical part for the CAD software.
Coils switch very reliably with 66 ohms in series on 5V supply, for coil at 3.3V / 26 mA
Coils are reliably reluctant to switch from rest, but will sustain free oscillation once started with 85 ohms in series for coil at 2.9V / 23 mA
Coils will not sustain free oscillation with 110 ohms in series for coil at 2.65V / 21 mA
This suggests a 2-input AND scheme with series resistors should be fairly robust with say 120 ohm series resistors, but while theoretically possible a 3-input AND with 200 ohm resistors might be fragile depending on relay variance and timing.
Just curious, how much current do you think the contacts can carry if they don't have to switch the current.
It is not in the TX2SA-L2-5V spec?
I'm interested in using this relay, (I bought a set to), as a small DC motor driver / speed control.
This PWM is done with a single MOSFET. Anyway, the relay does the reversing and the MOSFET guarantees there is no current flowing during relay operations.
I know that several times the name plate rating of current for motor starting current, maybe 6A, would be OK.
But the steady state non switching current info is hard to find.
Ya, another solar tracker. (It's a disease with me.)
Duane J
That said, if you don't have the arcing you will still have (most likely limitation) the wires linking the contacts to the pins. These are tiny relays and I'm pretty impressed that they are rated for 2A. If you've bought a reel, I suggest hooking one up to carry the current load you're interested in and measuring the voltage drop across the contact in millivolts. The higher it is the worse, because that's your contact and link wire dissipating power.
Since they're rated at 2A switching I'd guess you would be OK with 6A steady state. But I'd like to see the millivolt drop across the contact below, say, 30 millivolts -- that's about a tenth of a watt being dissipated in the relay, which is probably north of what the designers intended.
I'm not absolutely sure, but I strongly believe that you should switch a minimum current through relay contacts, at least to ensure their cleaning, BEFORE allowing them to fully conduct the maximum intended current.
Even in cases as the ones Duane J depicted above, when a MOSFET will deal with the current switching, after relay contacts were fully switched, IMHO its wise to pass a minimum cleaning current, before allowing the MOSFET to fully switch the maximum intended current level.
The minimum cleaning current and time expent allowing it pass through the contacts, will ensure a better path, when the MOSFET finaly switches the maximum intended one.
Even mechanical methods of doing such cleanup are possible.
Perhaps the following note could better explain the concerns that drove my thoughts.
http://www.ni.com/white-paper/7200/en/
I hope you could enjoy a better circuit operation this way.
Yanomani
P.S. There is also an excellent tech info from Panasonic, that depicts intetesting data about the relays and its contacts. Please, look at page 12.
http://www.panasonic-electric-works.com/peweu/en/downloads/ds_x61_en_relay_technical_information.pdf
DJ: I have always been tempted to build a solar array & tracker. If you're into it, I for one would be interested to hear about your experiences and projects.
All the Duanes in this Forum are the coolest!
Yes, I'm well aware of the problems of low to zero energy switching.
However, the TX2SA-L2-5V relays we have been discussing in this thread have Gold Clad contacts. This type of contact is, generally, not prone to low energy switching problems.
Your second reference goes into this in some detail.
Many years ago we had a computer, Univac at that time, that had hundreds of real nice miniature switches as logic inputs. B Box jump address for the history buffs. They had silver contacts rated for 120VAC. These things worked nicely for about a year or so when they started to appear high in resistance. A "good" switch in a bad application.
These switches required that spark to keep the contacts clean. Many thousands were replaced with the same switch but with gold plated contacts, (I don't think Gold Cladding was available), and never had problems again.
Anyway, I suspect these relays will work fine for my zero energy switching application.
Mine haven't arrived yet. But I will thoroughly abuse a few to see how good they are.
BTW, another method of making low energy switching work is called contact "Wiping", I think. Lots of relays do this. As the armature moves the contact slide over each other a bit to rub off corrosion products. You can see this in many open frame relays if you close them with your finger.
BTW, BTW, the best relays for low energy switching are the mercury wetted relays. Much more expensive but extremely low and repeatable contact resistance. I almost always require these in test equipment I design.
Duane J
I do sell one of my designs, 30,000 or so to date, but I do publish all the circuit so you could build your own and I will answer questions if you need help.
That being said, I have dozens of designs of designs many of which I publish. See:
Red Rock Energy
Trackers, my beginnings I am the guy that invented the use of LED as light sensors in trackers.
The future of tracking mounts
My commercial trackers
Very simple designs
Even simpler for solar cookers
If you have an AC power source
Non computer controlled heliostats
Something you have never seen
2/3rd motion heliostat
Tracker patents
LED sensor circuits
High precision PC based computational tracking.
I have a Props and Arduino based lower precision computational tracking too.
I've been doing this stuff since the mid '70s.
Ya, it's a disease with me.
Have fun, I have.
Duane J