adding delay to recessed wipers

1968 Olds Cutlass, 2 speed recessed. I've thought into this and I'm certain there is a simple solution to a finite problem. I would like to share my concept and receive feedback. The challenge is they are recessed blades or they park below the hood line when wiper switch is turned to off, which is a ground assortment with a mechanical park switch that leaves motor on until contacts open, removing ground coupling. A typical adjustable wiper delay works, but the blades cycle down into the park position at end of each run interval if a long enough delay is used and the wear and tear is not needed nor welcomed on a 45 year old classic. I want to connect something that: Interrupts the 12VDC supply for a variable duration and resume power again. Like turning the key off during wiper sweep then back on again. I will time when the unit cuts power to wiper motor by positioning a small magnet towards the outside diameter (about 4" Nylon) on the main gear of the wiper transmission. 1 revolution of gear makes 1 full wiper cycle, (over and back). With an adjustable position NO/NC reed switch mounted (proximity switch) it will be activated by the magnet when blades are in lowest position on windshield. The delay needs to open a relay (NC contacts for non-delay operation) disconnecting the motor from the 12VDC source and start delay countdown. At end of delay duration the signal to relay coil is removed thus returning relay to closed and reconnecting source to wiper motor, even though the reed switch is still sending trigger signal as magnet will still be activating reed switch. I could overcome the reed switch steady signal by coupling in some form of 1-shot signal modifier. I have ordered a reed switch with both NO/NC ability just in case. I intend to turn on low wiper switch and choose to turn on/off delay unit and adjust pause time at dash, meaning original operation and delay mode need to be seperate. I don't know how to link searched posts elsewhere in this forum, so may I reference these two I found here; www.the12volt.com/.../forum_posts.asp~TID~105221~PN~324 www.the12volt.com/installbay/forum_posts.asp~TID~127126 Thanks in advance

I had a similar problem and solved it with a simple 555 circuit. The off time was the normal variable inter-wipe delay, but the on time was adjustable using a trimpot. In my case the self-parking action was by motor reversal and that was defeated by setting the on time so that the wipers stopped just short of their normal end of sweep (only by a cm or 2). If that hadn't have worked I would have used the same circuit** but have the relay interrupt the motor's +12V supply, and I reckon that should work for you. You might be able to break it at the fuse if the wiper has a dedicated fuse. Neither solution requires any mechanical timing (position switches) but does assume a constant wiper speed. ** PS "same circuit" for the +12V interrupting solution EXCEPT that the relay sense changes, ie, instead of the normal intermittent being a relay in parallel with the motor's grounding parkswitch and closing to initiate a sweep, the +12V interrupt uses an SPDT relay with its NC contacts (30, 87a) in the +12V path; it's then the long intermittent delay that turns the relay on to break the +12V to the motor. IOW, interchange the longer (variable intermittent) delay with the short delay, or swap the GND or +12V end of the relay coil. But there are various wiring possibilities especially if +12V wiper supply relays are used (as they can be for arctic hardening - ie, to prevent motor burnout when wiper arms are frozen or seized).

Thanks Oldspark. I follow your suggestion. Problem being the wipers arenotconstant speed in varying conditions, I.e., wet, almost wet, highway, not highway, etc. Timing will get out of synch in short order. That would surely annoy me. My initial solution is some form of proximity switch. I'm not a schooled electronic tech. I have solved simple problems by looking at reference materials and circuit examples and been rather successful in the past but it has been awhile, like 10 years and more. An issue I come across with a 555 and 556 is the trigger needs to be momentary. The reed switch will not be momentary unless I can condition the signal to a 1 shot, thus that's why I even mention the 555. I am considering looking into whether multiple relays in a logic format might work. I'm convinced the solution(s) is commonly used in industrial motion control. Machine moves to make or break a proximity switch which invokes a relay to stop further motion and cause a timer count down action then then the relay resumes motion. Operators panel has potentiometer knob to adjust the delay duration and has an on/off switch. I've been analyzing this with my limited knowledge of circuits till my head hurts and then I fall over unconscious, only to wake up and do it again. What would a circuit need to be to take the NO or NC reed switch non-momentary signal and use it to change the power relay state from NC to open for an adjustable 1-15 seconds and repeat this series of actions? Again, thanks for considering putting your thoughts and experience into this.

Being variable speed you have the right idea - a 555 etc is no good for setting the (dwell?) timing. So yeah - some positional sensor unless you get into the guts of the park/retract mechanism. A magnet & reed, or maybe an optical sensing an arm position.

I think I can achieve what I need using some type of (1 Shot?) Time Delay Relay although I am finding it difficult to locate both a proper designation and source. 12VDC Coil/NC contacts SPST (or SPDT) Contact rating 25-35A preferred, but could drive a separate relay with higher rating. Delay duration externally adjustable from ~1 sec. yo 10-15 secs. (potentiometer choice) It needs to operate exactly like this: 1. NC contacts indefinitely. 2. Indefinite +12 trigger signal to coil is applied. 3. Relay Opens contacts and begins countdown, even with trigger signal still applied. 4. At time out, contacts resume closed state as at beginning, even with trigger signal still applied 5. Timer resets when trigger signal is removed from coil. I would like to ask for any information leading to getting the right relay. And, I'm hoping to find one that is reasonably priced, say <$30.00? Thanks

Standard automotive SPST & SPDT relays are 30A but 60A are not uncommon. (Be aware NC contact ratings are less than the NO contact ratings - eg, 25A & 30A; 50A & 60A etc. A 555 can supply 200mA but it's not difficult to add a transistor or MOSFET to boost that current. (Many 30A & 30A coils are 240mA etc.) A conventional 555 circuit won't work because the trigger signal (pin 2) must be removed for the timing sequence (output change), however there may be implementations that use other pins as triggers (pins 4 or 5 or 6?? - I'd have to review...) else maybe a capacitively coupled pin 2. If you're in to programming or game enough, I'd suggest a PICAXE 08 (eg, 08M2) - an 8 pin programmable chip with multiple inputs & outputs, counters, etc (a mini uPC) for ~$3 - $5. Instead of the 555 & its components, a PICAXE needs a 5V regulator (eg, 78L05 ~$1) and 2 programming resistors (from a PC serial port else USB-serial converter (~$25?)) and input & output circuitry. A typical output could be 2 resistors & a $2 MOSFET to switch over 10A. That's a big learning curve and investment (eg USB to serial) for a one off project, but if you ever have other projects... And whereas the 555 has a standby current of 10mA, the PIC 08M2 draws less than 14uA - not that that's an issue for an intermittent wiper circuit which is negligible compared to the wiper motor and only draws current when on. Alas I mention the latter (PIC) in a feeble effort to pass the buck to you . Otherwise I may have to understand what you are asking above, and then review 555 stuff (which I once used to know LOL!).

I have made some stuff when I was still doing RC Airplanes. Being an odd-ball, I made an various alternating LED Flasher for wing-tip nav lights, some didn't work the way I wanted, various flasher arrays, high end NiCad battery chargers gel-cell chargers, model finders, and the lot. I am game for anything. I'll see what pops up in the way of off the shelf TDRs. Hopefully someone involved with Industrial Motion Controls will have an idea on where and what to get for a electromechanical relay. If not, I'll be needing your input to viable circuit ideas using the programmable PICAXE. I probably have half a dozen 78LM05s and make my own pc boards, it'll be fun to get back into it for this. Thanks, Patrick

OK, Got it narrowed to this: Need source for 1 shot inverted delay relay, such as exactly like SSAC's discontinued 12VDC Externally Adjusted delay Normally Open Solid State Relay #KRD9131A. You can see it at http://www.galco.com/buy/SSAC/KRD9131A. SSAC.com shows an excellent animation of my needed relay function at http://www.ssac.com/animation/singlesh.htm Wishing to find substitute or a new unit in box on some suppliers shelf. Amperite.com is showing Hockey Puck 12VDC .2-20 secs NO #12D-.2-20-S-ST2. Hoping that might be a good choice. Any other devises you know of?

Not that I recall the "logic" needed for your application, but a few comments... I don't like solid state relays - especially for DC and automotive applications. That may be an antiquated view and maybe their "hardening" has improved, though it seems they are still prone to leakage thru their contacts (even though that may not impact your application). However that discontinued KRD9131A seems to be a normal mechanical relay with "front end" electronics (ie, solid state, but not IMO a "solid state relay"). The Amperite 12D-2-20-S-ST2 does seem to be solid state (as witnessed by its voltage drop of ~2.5V at ~2A). And it is only rated for 2A else 10A, and IMO even 10A may not be sufficient.    DEI manufacture various timed relays which have even impressed me (ie, I'm usually DIY but even I am tempted by their offerings!). However I am not familiar with their range though the DEI-528T is a popular unit that comes to mind. Maybe the DEI-528T else others might fit the bill? I'd have to re-digest previous thread info to make any other meaningful comments (apart from a PICAXE 08M2 with whatever standard relay...). Sorry!

OK, used Amperite solid state unit. Just driving SPDT relay. Added Delay circuit Works awesome! Couldn't be more pleased! Thanks for your time and responses oldspark!