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Sept 11, 2016 14:17:39 GMT
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Ive been looking at relay circuits and I'm now confused.
What I have at the moment is a toggle switch. This sends power to a switch on the gearbox. The gearbox switch lets the power go to the overdrive solenoid but only in 3rd and 4th.
What this means is when you pull up to a light and forget to switch out the overdrive (switch is on dash) you pull away and when you get to 3rd gear the gap is huge as it automaticaly give you overdrive as the dash switch is still on.
What I want is to set it up so when you close the gearbox switch by going to 1st or 2nd it automaticaly resets the dash switch.
So I would need a momentary switch on the dash and some kind of latching circuit.
I thought this would be simple but a quick look at relays has confused me.
Anyone understand all this?
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Last Edit: Sept 11, 2016 16:48:45 GMT by VW
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Sept 11, 2016 14:38:50 GMT
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Hi, What normally happens is the steering wheel attendant does it and there's a light on the dash to remind them, if there isn't a light wire one in. It's all part of the driving experience  Colin |
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Sept 11, 2016 16:48:12 GMT
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There is a light on the switch.
if the switch was on the gearstick it would be easier to switch off when you realise you have forgotten.
Ill come up with a way, just need to get my head round it.
Would be so much easier if it always reset back to off.
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Sept 11, 2016 17:03:51 GMT
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cant remember if there should be one or 2 limit switches on the linkage, one that cuts the power to the solenoid in 1&2nd and one that cuts it in reverse gear, its ok to use the overdrive in 1&2nd but the output shaft can snap where the speedo gear sits, if it operates in reverse then I'm pretty sure it smashes it to bits!
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Sept 11, 2016 17:25:18 GMT
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Yep.
My box just has a switch on it that only allows power in 3rd and 4th.
No need to use overdrive in 3rd, I guess it was just easy to make the switch that way.
I just want a momentary switch that activates a latching relay.
It also needs to release when power is cut too though.
Could do it with logic I guess, create a little 5v supply.
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Rich
Club Retro Rides Member
Posts: 6,256 
Club RR Member Number: 160
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Sept 11, 2016 18:01:14 GMT
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This should work. When the 3/4th switch is deactivated, it'll reset the relay to it's unlatched state. O/D will still then only be trigger-able in the correct gears. And its very simple to wire.  Sorry, got the switching terminals the wrong way. It's now correct. |
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Last Edit: Sept 11, 2016 18:05:51 GMT by Rich
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Rich
Club Retro Rides Member
Posts: 6,256
Club RR Member Number: 160
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Sept 11, 2016 18:08:23 GMT
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Also, what is the shift pattern? There are a lot of late O/D cars with a switch built into the knob. Although I get the feeling we have covered this, but I can't recall if it was for your van or something else.
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Sept 11, 2016 18:14:38 GMT
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So with the gearbox switch closed, power from the momentary switch activates the latching relay. Will a second push of the momentary switch release the latching relay or will it only release once power is cut from the gearbox switch?
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Sept 11, 2016 18:15:42 GMT
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Thanks by the way.
It prob was me about the shift pattern. 4 speed with reverse left and up.
Same as volvo I think.
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Rich
Club Retro Rides Member
Posts: 6,256
Club RR Member Number: 160
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Sept 11, 2016 18:19:45 GMT
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So with the gearbox switch closed, power from the momentary switch activates the latching relay. Will a second push of the momentary switch release the latching relay or will it only release once power is cut from the gearbox switch? I believe a second push will also deactivate but that depends on the brand of relay I would guess. Usually they should one-push de-latch too. Worth checking. |
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Rich
Club Retro Rides Member
Posts: 6,256
Club RR Member Number: 160
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Sept 11, 2016 18:25:10 GMT
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Sept 11, 2016 18:29:42 GMT
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Thats great, thanks. There expensive in 12v! I used some 5v ones in a pre amp and they were buttons, even for mercury wetted. Worth it though to not have the frustration of the engine falling on its  whenever you forget to disengage after changing down. |
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Rich
Club Retro Rides Member
Posts: 6,256
Club RR Member Number: 160
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Sept 11, 2016 18:36:28 GMT
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Hm, might be worth just checking that the Relay WILL reset after terminal 30 is de-energised. I'd drop an email to check. Otherwise It may not work as planned.
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Sept 11, 2016 18:53:47 GMT
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Ill check but it will need to get its energy to energise the latch coil from somewhere.
Ill send them an email.
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Sept 12, 2016 18:34:43 GMT
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Maybe check if there's any standard car unit you can use? The high/low beam on my 1972 Beetle (1303 ?) was very similar to what you want. With headlights on - a flash toggles to high beam - flash again to toggle back to dip beam. The high-beam flash controlled the toggle, I don't think it was the stalk so it must be something else (relays?) turn lights off and when you turn on again - they always come on dip-beam. Could you use a lighweight (cheapish  ) latching relay to feed power to a normal (very cheap  )relay? www.maplin.co.uk/p/12v-dc-2a-dpdt-miniature-latching-relay-n38aw  |
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Sept 12, 2016 18:35:52 GMT
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Turns out that relay is no good. Its changeover and mechanical latching so if tou cut power (gearbox switch) if stays latched in that position.
I think ill pop down local auto electrics place and see what thay say.
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Sept 12, 2016 20:07:05 GMT
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Sept 12, 2016 20:24:07 GMT
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I don't think that will work. It would require two dash switches.
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Sept 12, 2016 20:46:56 GMT
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Ive been looking at other modules on ebay though, some of them might work. I just need to find one without memory.
I just need push trigger once, output goes live. Push same trigger again, output goes off but if the main power supply goes off output automaticaly reverts to off.
I can find lots of modules that are simple push on push off latching relays but they all seem to have memory so they revert back to previous state.
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steveg
Posted a lot
Posts: 1,565
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Sept 12, 2016 21:05:01 GMT
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I wired up my Triumph 2000 to have overdrive in second but never thought of making it disengage. The gearbox is quite well spaced so having and extra gear between helped acceleration a bit if you could switch it OK while changing gear. It did slip a bit on overdrive second with the 2.5 engine I fitted though.
If you could get it to disengage every time you changed gear and then engaged with a button or column mounted lever that would be great.
Volvo fitted overdrive on some of their automatic cars, think 740's and 940's and I wonder if they have some sort of circuitry.
What about a clutch mounted switch that disengages overdrive every time you operate it ?
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) latching relay to feed power to a normal (very cheap 
)relay?
