Ignition system for Farm Boy

[simonbirt]

I am building a Farm Boy hit and miss engine which is progressing OK- huge quantities of swarf so far.

I am now starting to think about an ignition system, I quite like the idea of building my own. Electronics is not really my thing but I do have a basic understanding and have made a few circuits in the past. It would be useful to learn if others have gone down this route.

Regards,

Simon

 

[deverett]

If you do want to have a go at soldering up your own module, have a look at Jerry Howell's offerings:
http://www.model-engine-ignition.com/home/ignition-modulesYou won't have wasted too much money if things do go wrong!

Next step if that fails, have a look at the replacement ignition modules sold for the Chinese hi 'n' miss engines:
eBay UK 372664264988. That is the route I'm taking for my present project.
Or Roy Scholl at S & S, but it looks like you have to be quick: Roy's CDI Ignition Systems

Dave
The Emerald Isle

 

[doc1955]

Yes I build my own ignition units a good place tostart if you want to do your own is to usr one of Jerry Howells or if you can still get one of Roy's cdi either will work great for what you want. Here is a video showing the ones I build.

 

[coulsea]

Next step if that fails, have a look at the replacement ignition modules sold for the Chinese hi 'n' miss engines:
eBay UK 372664264988. That is the route I'm taking for my present project.

Dave
The Emerald Isle

I don't know about that particular chinese ignition but I do know that quite a few cheap ones have problems. I can recommend the rcexl units. ebay uk 173851217006

 

[doc1955]

I purchased this one to just check it out and see how well it would work. Well the first one did not work at all but after a few e-mail back and forth they sent another that seems to work well. I never did put it on any of my engines I still prefer the ones I build. But anyway you could try one and see if you like it or not. For around $20 it's not a bad price.
PS they have it labeled as a glow plug but it is a cdi unit.

https://www.stirlingkit.com/collect...l-engine-rc-plane-ship-car-model-engine-model

 

[Tim Wescott]

You could always go with a Kettering (points, condenser & coil)! That's pretty easy.

 

[deverett]

I don't know about that particular chinese ignition but I do know that quite a few cheap ones have problems. I can recommend the rcexl units. ebay uk 173851217006

Have you tried one of these on a hit 'n' miss engine? Reason I ask is that I note they have auto advance and I was under the impression that this was not suitable for hit 'n' miss engines. (hearsay only, not practical experience).

Dave
The Emerald Isle

 

[coulsea]

Have you tried one of these on a hit 'n' miss engine? Reason I ask is that I note they have auto advance and I was under the impression that this was not suitable for hit 'n' miss engines. (hearsay only, not practical experience).

Dave
The Emerald Isle

Yes I do have them on hit n miss engines and they seem to work fine. I have found it difficult to find out the specs for the auto advance but some on the plane forums suggest that the spark is constant between 450 and 4000 revs (or maybe 2500). I can start them with a good flick of the flywheel. A hit n miss will only fire in a fairly narrow rev range by design.
I haven't tried any other type of ignition so would be interested to hear what others say.

Andrew

 

[bluejets]

Below is a multi spark kettering ignition, easily used with points.
Problem usually is getting a hold of small kettering ignition coils as most small engines these days use CDI and not suitable for points ignition.

I found the circuit can be used with a Ford BA Falcon coil and quite ok on a single 18650 2500mAh 3.7v Lipo cell.

Doc uses the same board and he uses 6v and a dropping resistor.
He might be able to help you with the type of coil he used and where to get one if you are in the US.
Although just more bits to go wrong, more than likely he is just using what he has on hand.

Below are a few pics and some files if you want to build your own or get a mate help you out there.

Of course, the electronics board is not essential as a 3.7v Lipo, a BA coil, a set of points and a condensor would be just as good.
Plenty of basic kettereng system drawings around on the net.
I use a 0.47uF 400v capacitor from any electronics store across the points.

Advantage of the electronics board is, if the engine stops with the points in the coil saturation position, it will time out and shut off after a short period, thus saving your battery power.
Then again, most of these engines run under some sort of supervision so any shut down not really necessary.

 

[simonbirt]

Thank you all for your help and advice. I now have a better idea of what is needed, leaning toward building one. I am in the UK so will see what can be found coil wise. I assume a motorcycle one may do the job?

 

[elliot9797]

I have used a International Harvester Farmall A,B,C,H,or M coils. Work great, and cheap

 

[mrehmus]

Here is how I mounted my Sage ignition board in the bottom of my GEM-1 box. I triggered in with a reed switch mounted in a brass tube. The coil is a Ford Coil-over-Plug which works fine with 12 volts as in this setup down to approximatelye 6 volts with 4 AA batteries. 12 volt gel-cell is in white 3D printer box under the ignition circuit.

 

[doc1955]

I use 12v coil packs and step up the resistance. You need to run the resistance over 1.2ohm or you run the risk of frying the 555 timer or the TIP 120 chip. I run mine with 6V and I use the spark saver (2 hall sensors) but it will work fine without the spark saver the spark saver just saves on battery life. I also put a heat sink on the TIP 120 on engines I run at a higher rpm. You shouldn't need it though on a hit miss.

I have also used the TIM6 circuit and step up the resistance in the coil the same only thing with this circuit is if your engine stops on the magnet you run the risk of frying the TIP42 chip.
Anyway I have had good luck with both. Good luck


PS
I order my 555 chip of of ebay just look for 200mA I think I got 10 for around .50 each. I also get my other IC chips there usually can get them for a lot less than at any electronics store.

 

[74Sprint]

Below is a multi spark kettering ignition, easily used with points.
Problem usually is getting a hold of small kettering ignition coils as most small engines these days use CDI and not suitable for points ignition.

I found the circuit can be used with a Ford BA Falcon coil and quite ok on a single 18650 2500mAh 3.7v Lipo cell.

Doc uses the same board and he uses 6v and a dropping resistor.
He might be able to help you with the type of coil he used and where to get one if you are in the US.
Although just more bits to go wrong, more than likely he is just using what he has on hand.

Below are a few pics and some files if you want to build your own or get a mate help you out there.

Of course, the electronics board is not essential as a 3.7v Lipo, a BA coil, a set of points and a condensor would be just as good.
Plenty of basic kettereng system drawings around on the net.
I use a 0.47uF 400v capacitor from any electronics store across the points.

Advantage of the electronics board is, if the engine stops with the points in the coil saturation position, it will time out and shut off after a short period, thus saving your battery power.
Then again, most of these engines run under some sort of supervision so any shut down not really necessary.

This is probably one of the best small low battery voltage ignitions I have seen. The 555 timer can be modified to work very similar to almost all the electronic HEI ignitions used through out the world of distributor type engines or 1 cylinder, or 2 cylinder wasted spark. For example the GM-Ford-Chrysler HEI works with a inductive pick-up, the coil starts to charge when the pulse voltage starts to rise (going positive) and fires the coil when the pulse starts to go back to zero volts (going negative). No positive going pulse, no coil charging. By using the 555 timer one can adjust the dwell time to suit the coil.

Ray

 

[74Sprint]

Auto advance can be done in several ways: #1 use the negative going side of the pulse. As the RPM increases the pulse width will decrease but, the start of the pulse will never change. Only the trailing negative going edge changes. If one uses the negative going edge, the timing will advance automatically with increasing RPM but, only to a limit which can be controlled. #2. Some manufacturers use something like a small preprogrammed PIC micro controller with a fixed advance curve. #3. Same as number 2 but with a programming interface to change the advance curve. Of course as the complexity increases so does cost but, each circuit can be modified to suit one's needs and funds available.

Ray

 

[simonbirt]

Below is a multi spark kettering ignition, easily used with points.
Problem usually is getting a hold of small kettering ignition coils as most small engines these days use CDI and not suitable for points ignition.

I found the circuit can be used with a Ford BA Falcon coil and quite ok on a single 18650 2500mAh 3.7v Lipo cell.

Doc uses the same board and he uses 6v and a dropping resistor.
He might be able to help you with the type of coil he used and where to get one if you are in the US.
Although just more bits to go wrong, more than likely he is just using what he has on hand.

Below are a few pics and some files if you want to build your own or get a mate help you out there.

Of course, the electronics board is not essential as a 3.7v Lipo, a BA coil, a set of points and a condensor would be just as good.
Plenty of basic kettereng system drawings around on the net.
I use a 0.47uF 400v capacitor from any electronics store across the points.

Advantage of the electronics board is, if the engine stops with the points in the coil saturation position, it will time out and shut off after a short period, thus saving your battery power.
Then again, most of these engines run under some sort of supervision so any shut down not really necessary.

Have decided to build the electronic version as I don't want to use points. I have or can source all the components, except I am having trouble with the Q3/Q4 transistors, can't find a 3030T. Is there an equivalent or am I looking in the wrong place. I am in the UK.

 

[Tim Wescott]

1. Don't buy electronic components off of eBay (Sorry @doc1955) At least not common chips like the 555 -- you can get them cheaply from real mail-order suppliers. DigiKey, Mouser and Newark in the US, Farnell (I think) in the UK. Counterfeit chips are a thing, you can trust a distributor, and it doesn't cost all that much more than eBay.
2. I'm not sure what a 3030T is, but there's plenty of Hall effect sensors out there. Some of them are even designed so you don't need to make a custom board just to mount them. Here's a plethora of them from DigiKey, all of which should work. You want to look for sensors that are:
   1. Bipolar or omnipolar (works with the magnet pointing either way)
   2. Through-hole mounting (so you can solder wires to the leads)
   3. Open collector or open drain (so it acts like an open switch with no magnet)
   4. Will stand a power supply voltage of 6V or more

 

[bluejets]

Have decided to build the electronic version as I don't want to use points. I have or can source all the components, except I am having trouble with the Q3/Q4 transistors, can't find a 3030T. Is there an equivalent or am I looking in the wrong place. I am in the UK.

KY-003 hall effect modules will work ok.......already mounted on a pc board with an LED and resistor on the collector.
If you want to roll your own , then I use Allegro A1120 but pop a tiny cap right on the base of the hall effect supply pins (0.01uF)
Or use 3144 same as on the board of the KY-003.
20PCS SENSITIVE HALL-EFFECT SWITCHES SENSOR SIP3 OH3144 3144OH A3144E A3144 3144 | eBay
Contrary to some comments about Chinese electronic clones etc. , never had a problem, mostly old wives tales.

 

[simonbirt]

Thank you all, I am much wiser than before. I will let you know how it turns out.

 

[Bernett1]

I’m new to this group. I don’t have the expertise or equipment to build engines but I really love the work this group does. I am using converted 2 stroke engines for RC planes and wanted a less expensive CDI system than the rexcl systems. I have purchased a 4 pin dc scooter CDI system and a scooter coil. I anticipated the same issues of using a standard hall sensor and not being able to trigger the CDI unit. I did some searching and located some inverted hall sensors. There aren’t many of them. I purchased some melexis us5683 hall sensors. They are unipolar inverted hall sensors. They should be low to high when they come in contact with the magnet. I don’t have all the components so I haven’t been able to test the system. My question is do you think thes inverted hall sensors will work and if I’m using a 3s lipo battery to power the CDI system can I use the same battery to power the hall sensor. I’m thinking the CDI trigger is just looking for positive voltage and it doesn’t matter if it’s .5v, 5v, or 12v. Do you think I am correct in my assumption? Thanks.