Thinking about this some more here. If I understand what you guys are currently doing, then I think I will go ahead with this little project.

From what I've read, you guys are trying to reduce the pulsewidth enough to reduce the heat buildup in the ignitor, is that right? If so, then maybe putting a CPU heatsing/fan on the ignitor would control the temperatures better without reducing the length of the pulsewidth.

Have I got this right, or are you guys working along a different path altogether?

 

that might work if u can find those fans that will run on DC power. those in PCs use AC.

 

There are DC cooling fans available.

I found a bunch of 80mm DC cooling fans... that might be too big?

I'm sure you could find smaller fans.

 

Fans in pcs are indeed DC

 

Confirmed. PC's put out a 12v and 5 volt circuit. A 12v fan should work fine.

To bad you guys in the states don't have Princess Auto. They have hundreds of variations of these fans in tons of sizes, and they're usually $1 - $9 Cdn.

Another idea that might work to keep that pack cooler is to put it in some airflow from the grill. You'd have to relocate the pack and extend the wiring though....

 

hey guys, i dont think air is going to transfer enough heat here. There is already some decent airflow under your bonnet when the car is running - would be much more than what a dc fan will provide.

The problem is we are charging the coil for too long, it enters current limiting mode and the ignitor heats up a lot.

The ideal solution is to fix our circuit so it doesnt overcharge and enter current limiting mode.

I guess something we could do to minimise impact is take the heat away from the ignitor - Rob and I have used aluminium, wedged between the coilpack and mounting bracket to help take the heat away.

So far so good, however the real problem is still there and once directly solved will not be a problem Just waiting on Kent's equipment to arrive

 

Yep. Exactly. We need to fix the source of the problem instead of the symptoms. There is a lot of heat generated in the ignitor and ballast resistor. Sure, a fan will help some, but serious cooling is really needed without fixing the circuit (like a large liquid cooled heatsink). The other option is too increase resistance in the circuit with an additional ballast resistor to limit the current flow.

I believe the o-scope is on its way and should be here this week. My other stuff from the US was shipped the 12th and should be here any day. It is hard to know exactly with international stuff. It shouldn't take long to see what is going on once I have the equipment. Once we know what is happening, it should be easy to find a solution.

Ken: Yes, that is what we are doing. The new circuit limits the pulse correctly without the coil pack connected. With the coil pack, there is some strange behavior that we are trying to track down the cause of. Limiting is the best solution. Once the coil becomes saturated, the ignitor goes into current limiting mode. Beyond this point, the coil does not charge any further and the incoming energy must be removed as heat through the ignitor. So, we want the coil to saturate for best performance, but beyond that, all the extra pulsewidth does is create heat and shorten ignitor life.

 

Hey guys,

I got the stuff from my dad and the o-scope today. There may be a problem with the o-scope. It wasn't packaged very well (just a box, no packing material). The screen cover is broken and the rear part of the case is cracked. This doesn't bother me, but the scope is being a little weird on its function. Sometimes the traces do not go across the screen completely. Also, it seems when it does this, the voltages do not register correctly (I put in 12v DC, and it shows like 6v). Also, trying to figure out the trigger on this machine. I have contacted the seller and see if he can help (like if there is some trick that I am missing). I will continue to mess with it and see if I can get it working correctly. Then I will be able to test the circuits.

Kent

 

who on earth ships out an oscilloscope without packaging it???

 

Exactly. It was just stuffed in abox that was about the same size as the scope. Nothing to protect the scope at all (especially the front). The box has marks from where the corners of the scope were cutting into the cardboard. Like I said, I don't care about the screen cover or the back being cracked. Just want it to work correctly. I dunno. Maybe he was trying to save on shipping costs. He only charged 15 Euro for shipping (across most of France) and the thing is very heavy (probably 35+ lbs). I think if I can get it working correctly, I will resell it on ebay after the circuits are all sent out. It is way too heavy to consider shipping to the US. I will just by another scope when I return.

 

Okay. I opened up the scope. I found that a couple wires that plug into one of the circuit boards were knocked off during shipping. Now the traces go across the screen. It still seems that the voltage isn't measuring correctly (12v showing as 5-6v). It is late here, so I will play with it some more in the morning. It does this on both channels.

 

There are more of them out there!

I once had someone courier me a poster without putting it in a shipping tube. When I called to complain I was told that it wasn't crushed when it was shipped...!?

And then there was the time I received a shipment of 20 or so CDROMs in a box without any shipping material. I just rejected the whole order on the spot...

 

Well, I don't have much hope for this o-scope. The traces pretty much don't work at all now. Now they show as 1" vertical marks near the center of the screen. I've contacted the seller, but it is a little difficult because he only speaks french (I think) and my french is pretty limited. Maybe I can write something and have one of the french canadian guys check it over (Jon?). I am not sure if the seller understands the problem. His says it functioned correctly when he shipped it. I guess I can only hope for a partial refund or something and sell the current scope for parts and buy another scope, I guess. I don't have the time/tools to try to fix this scope here. I was really hoping to find the source of the problem and get the parts on order. I will be out of town for nearly 2 weeks in the first part of May. I guess I can order another scope before I leave and have the seller ship it a few days before I get back so that it will arrive when I return.

Well, hopefully we will get this sorted out soon. Again, I am very sorry for the delays. It has proved to be difficult getting stuff here, getting things tested, and so on. It probably would have been easier to wait until I got back, but by that time many of you guys would be putting your cars away for winter.

Kent

 

Kent,

I'm sorry to read about all of the troubles you're having. The last thing I want to see is for you to have to absorb a lot of extra expense & hassles trying to get the circuits out to us. I may not be speaking for the rest of the people who ordered one, but I don't have a problem waiting for my circuit until you get back home. Maybe the others who placed an order will chime in and give their opinions on waiting until then.

 

Thanks, Dave. I do want to get them out and I am sure you guys are wanting to get them. The extra cost is not bad thanks to ebay. It just sucks to buy something, wait for like 2 weeks to get it, and have it be broken. Hopefully I will have some better luck with the next one. I don't think I could wait to send these out even if you guys wanted to wait. I have been spending a lot of time thinking about the problem since I found out about it and want to get it solved. With the proper (functioning) equipment, it should be real easy to see what is going on.

I hope I didn't come across as wishing I hadn't done these here. That is not the case. I enjoy doing electronics and it gives me something fun to do when not working (don't have my 7 to fix/drive ) It is just more challenging to get the things you need over here compareed to the States.

I will keep you guys informed. Maybe if I can find a scope near here, I will just get on the bus/train and pick it up personally.

Kent

 

No problem I know you want to get this done, but I didn't want you to feel obliagted to finish the circuits in a hurry. I know you have a full plate being at work overseas. I'm glad you are still having fun with the project, though - that's what really matters.

 

doesn't it suck that you usually need the same tool you need to fix that same tool? fixing osciloscope with another one ... I really wish i could be helping out more right now ... but it is coming to an end fo the school year and I have tons of things to study for, and project to hand in ... i'm done this friday so hopefully i can be better of assistance after this.

 

Couldn't you find a PC based oscilloscope that would be much more durable during shipping. Ebay looks to have some for not too much money.

I'm sure that you could get some contributions to help with the costs.

RXDad

http://www.picotech.com/index.html

 

Thanks. I am trying to find the best solution. I just got back after being out of town. I do like regular analog scopes and shipping shouldn't be a problem with proper packaging. Another option is a PC based scope like you listed. These should work fine. I am not sure of the best one to get. We don't need anything fancy as the frequencies are quite low. We do need enough sensitivity to show the noise. The third option is to use one of the software packages that let you use your computer soundcard as a signal generator/o-scope. The only problem with this option is that the soundcards can only handle like +/- 1v, so I would need to build a buffer amp and divide the voltage by say 10. This would be pretty easy, but I think I would prefer a pre-built solution for time sake. It sucks not even having RadioShack around to get these simple components to build testing circuits. I will keep you guys informed. The guy that I bought the scope from has not responded about some kind of compensation for the damaged scope. I guess this will be the first time for me to leave negative feedback on an ebay seller. Although, it wasn't totally his fault (bad packaging, but the shippers did the actual damage).

There are a couple o-scopes on ebay in France ending within the next couple days. Perhaps I will buy one and cross my fingers that it doesn't get damaged.

Kent

 

good to hear back from you ... thought you lost all hope ... welcome back home to the forum

 

Nah. I don't give up easy. It is good to be back. I was beginning to have rx7club withdrawals. If I can find a scope nearby, I will hop on the train and go get it personally. I certainly don't want to keep replacing scopes due to shipping damages. Some of the USB based scopes do look pretty cool too. The USB ones would be alot easier for me to take back to the States as well. I will see what I can come up with.

Once I find a solution, I will have one of you guys do the modification and try it on the car. I have the 2nd gen coil, wires, plugs, and so on here to test the circuit, but I don't have a 7 to test how the circuit works in an actual car.

 

SO is this the longest thread in the history of the Rx7 club? I'm actually looking forward to assembling one of these boxes (the trick) Doesnt look to difficult. One question however: Where did u find the nice little box to fit the circut board in?

 

Well, maybe for the 1st gen section. The basic circuit is real simple. The only drawback is the overheating of the 2nd gen ignitor due to the long pulsewidths. An additional ballast resistor may help this problem, but limiting the cause is the best solution (what we are doing now). The circuit that does this is a bit more complicated, but could be built on your own. The PCB makes it much easier, though. For the current boxes, I got them at www.mouser.com. However, it doesn't make sense to mail order only one part. Radio Shack has some pretty nice project boxes. The one I like is 3"x2"x1" from RadioShack. It is a black plastic box and comes with both an aluminum top and a matching black plastic top. The part number is #270-1801 and costs $2.29. Should be carried in stock at your local RadioShack. I used these boxes on the 1st couple circuits I built.

Kent

 

Just a quick update. I am checking through the old oscope to see if I can fix it. There seems to be a problem somewhere in the power supply portion. I found 1 internal fuse to be blown and a second fuse that was blown but someone had wrapped small wire around the fuse for a conduction path. Basically the connections to these 2 fuses are pretty much symmetrical. They are likely to generate say +/- 12v. I also found 2 blown diodes on the side with the blown fuse. I don't think the blown diodes are the cause, but probably and effect of whatever is overloading that circuit.

The wiring is from the transformer (drops the 220v main voltage to say 12v AC), passes through diodes to rectify (gets rid of the negative part of the AC), then goes through a large filter capacitor. From there it powers two circuit board cards and goes to the collector of a large transistor. I checked the transistor and it is fine, but with the collector wire connected, the results are a bit strange so it must be something in the wiring to the transistor from the diodes/fuse/etc. I'll mess with it more tonight and see if I can come up with something.

It is a little hard to track things down as there are many circuit boards and wires in there and I don't have a manual/schematic for this scope. I will mess with this scope until the auction ends on the oscope that I will try to buy. If I can fix this one, then great. If not, I will get another. It is a little difficult because I don't even know where to buy fuses and stuff around here. They are just the cylindrical glass fuses (2.5amp, 250v). I really need to find some fuses so I can test this thing.

Kent

 

Okay. I just bought another scope. Wish me luck with it. The old scope seems to be beyond repair. I will probably strip it for parts.

Kent