I am wondering if the 60V, 7A or 30V 11A Solid State relays could be used to charge an automotive ignition coil. Charge time would 2.5 to 3 Milliseconds. Using 3.3V, approx 10mA as signal. Battery Voltage would be 10 to 12 volts. Being that the coils are like an AC transformer but operate in DC mode, primary charges then when V+ Grounded or off the Secondary (high voltage) fires across spark plug to ground. I realize that I will have to use a flyback diode or some kind of suppressor. Read yor LC Blog Blog post, but have not yet calculater back EMF on primary side.
What is the time to turn the relay on and the time to turn it off?.
A number of circuit examples can be found on the web that simply use a Darlington transistor or MOSFET to drive an automotive ignition coil. Why do you want to use an SSR?
This example was attributed to EDN (you don’t need the 555 portion):
I want something reliable and inexpensive. I have seen some MOSFET and IGBT drivers and DIY Drivers available. Pololu has some dual channel motor drivers that might work. An advantage of the solid state relays is that they maybe be optical and no chance of damaging microcontroller. I just don’t know their speed in on and off.
Electromotive used to build what we are thinking about, a programable ignition system. I think that Covid must have put them out of business.
As Jim mentioned, the turn-on/turn-off times for solid state relays are typically around 1ms, and this holds for ours. You can find more specific information for our solid state relays in their descriptions and under the “specs” tab of the product page.
By the way, the ignition coil driver circuit from EDN posted above was obviously designed by a professional and appears quite sound.
In particular, the BU323Z Darlington transistor is specifically designed to switch automotive spark coils (among other similar applications), and has a built in 360V transient clamp. BU323Z data sheet.
Better tell you what this is being considered for, a 70s 914 Porsche programmable ignition using an Adafruit M4 Metro microcontroller. Presently the 914 is broke, its aircooled VW Type 4 motor has a valve seat dropped, a couple of pushrods needing replacing, etc. It is fed by two Weber two barrels in a individual runner setuo, SSI heat exchangers (close to equal length) going to a Bursh tri y type setuo exiting trough a turbo style muffler is the exhaust, With the bad cylinder off and turning the motor, the lifter movements indicates a performance cam. Ignition came from either Bosch 009 or 050 centrifugal advance distributors. 009 has full advance at around 3000 with full advance coming in at around 3500 RPM. All of this, resonance pressures intake and exhaust, big cam overlap, ignition timing can give spark knock from 3000 to 4000 if timed for 33 to 35 degree full advance for max power. A programmable ignition would solve this.
The most important of the “We” is the car’s owner, who I suspect doesn’t have deep pockets. My buddy, the shop owner, says car owner wants a set of used heads instead of new casting. Buddy’s thinking is 50 years of heat cycles may be weakening the castings.
Jim, appreciate EDN, circuit and BU323Z Data. I am not really wanting a DYI fab everything piece. Will pass that on. Another "We , semi retired EE who helps my buddy with electrical wiring and troubleshooting in restorations may appreciate.
Patrick thanks for info and pointing me to Specs. 1 ms with even 2% resolution may throw timing off 2 or 3 degrees up around 4400 to 4600 RPM. Since inexpensive and isolated, may buy some of the optical SSRs to have on hand. The specs thing got me looking more at G2 motor controllers. In some of the documental on PWM driving saw 5microseconds needed for recovery. Can live with this.
As of now it appears that if any ignition upgrades are considered it will be a CB Performance Black Box. This uses the stock distributor with timing advance locked. The advance is programmed in varying with rpm and vacuum. Low price with all cables included. The Black Box has been out 12 to 15 years and has gotten firmware improvements thoughout its life. Sure thank everybody for advice.
