1
\$\begingroup\$

I have built the circuit below and am trying to get the lights to go into wig wag using the relay (wig-wag is often used in emergency response vehicles with red and blue lights flashing or orange lights). I am getting my op amps to create a decent sine signal that should throw my relay on and off but it is not doing so.

I also want to implement a way to make the lights stay on at the same time and stay off using some sort of switch. I believe with the lights tied high I should be able to tie a switch to ground and use another to disconnect the switches from the relay.

"A wig-wag is a device for flashing an automobile's headlamps at a preset rate. In its traditional form a wig-wag constitutes the illuminating of the right and left headlamps alternately, with each lamp lit for around half a second at a time." source:source link

Circuit Diagram

\$\endgroup\$
  • \$\begingroup\$ Could you explain what 'wig wag' means? \$\endgroup\$ – Hearth Apr 27 '18 at 18:12
  • \$\begingroup\$ Start with adding a free-wheel diode to the relay. Then use a standard square generator to control the relay. You need only one Op-Amp for that. (The internet is your friend). I also suggest you use a FET or BJT to drive the relay. Your Op-Amp does not have enough power. \$\endgroup\$ – Oldfart Apr 27 '18 at 18:18
  • \$\begingroup\$ wig-wag is the term used to describe the alternating of lights, for instance on a police car or emergency vehicle. I would prefer not to use a function generator because most cars do not have the capability to output an ac signal like that. I am trying to use the two op amps to create an oscillator to power the relay and provide a duty cycle to make the lights go on and off with similar timing. I should be able to boost the OP amp power shouldnt I? \$\endgroup\$ – Preolt Apr 27 '18 at 18:23
  • \$\begingroup\$ Huh? What does it mean for lights to "go into wig wag"? This question is unclear. \$\endgroup\$ – Olin Lathrop Apr 27 '18 at 18:25
  • 1
    \$\begingroup\$ Don't tell just me. Put that into the question. \$\endgroup\$ – Olin Lathrop Apr 27 '18 at 18:42
1
\$\begingroup\$

I used to build these for the RCMP in my small home town when I was a youngster. Darned simple: a Tridon Electronic Flasher with alternating outputs and an automotive-grade SPDT toggle switch (25A contacts).

The particular Tridon Electronic Flasher I used was similar to the standard signal light flasher (two terminals) but this one had 3 terminals. One terminal was Normally Closed, the other was Normally Open. The On/Off toggle switch disconnected the load from the flasher NO terminal and instead connected it to the input Hot terminal of the flasher. The flasher does not operate if there is no load connected to the NO output terminal - thus the load connected to the NC terminal always had power.

These Tridon flashers were sheer magic to me when I was young. The relay coil has a bifilar winding and a large non-polarized electrolytic capacitor. Circuit operation is such that the relay contacts are OPEN until the capacitor charges. When the contacts close, the charge on the capacitor keeps them closed for the appropriate time period. Wire size of the windings (DC resistance) and the capacitor value determines the time constant. Brilliant engineering!

The reason I was making these for the RCMP is that the little potted modules supplied for their headlight wig-wags had a distressingly-short lifetime. My solution was much less expensive and much more reliable - the Tridon Electronic Flashers have a current rating of something like 25 Amps. All that current is switched with insanely-reliable relay contacts instead of wussy little bipolar transistors. Keep in mind that this was the mid-to-late 60's.

Tridon Electronic Flashers are still available. Although I don't recall the part number of the device I used to use, I'm thinking that the HD13 might be the correct part. But I don't have one at hand to check.

\$\endgroup\$
  • \$\begingroup\$ Really cool story, thanks for sharing Dwayne. What would you suggest for my circuit to build one of these in Pspice and test it before I try constructing it? Should I stick to my design or scrap it and try for a super large capacitor to provide the duty cycle I want for the lights? \$\endgroup\$ – Preolt Apr 27 '18 at 19:33
  • 1
    \$\begingroup\$ Easiest is a CMOS 555 timer chip driving a transistor or MOSFET driving a relay. Be sure to choose a relay with appropriate contact rating. \$\endgroup\$ – Dwayne Reid Apr 28 '18 at 19:17
1
\$\begingroup\$

Ya'll are making this way to complicated. Here's the easiest & quickest wig-wag relay design out there. Go to Autozone, pepboys, Advance or wherever & they will have what you need. Get a SPDT relay(novita rl45 is what I use) & get a heavy duty flasher relay(novita long life 555 20amp is what I use) I use a 2 prong flasher relay. this design only flashes back & forth. to double flash on each alternation requires a 3 prong flasher & 2 SPDT relays & can get complicated. now wire the X prong of flasher to a small blinker bulb to put a load on the flasher or it won't work & hide it somewhere outta site. now wire the other prong to the 30 prong of relay, 86 gets fused continuous power. 85 ground, 87 (Normally open) to positive lead of one light, 87a which is the middle 5th prong(normally closed)goes to other light. depending on . what will happen is when u switch on the relay the switched power to the SPDT will be getting turned off & on by the flasher causing 87 & 87a to alternate. another great project is a IR strobe like emergency vehicles use to make lites turn green

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.