I'm having trouble with my engine running the CH ignition module....

If my battery is running a little low, will it cause the module to stay at full advance?

It doesn't seem to want to retard the spark at startup if my battery is getting down around half charge area

Hi,
Your best bet is to call call CH. They might tell you to send it in.

Dave

I have come up with a solution to my problem.. when my battery was at full charge everything worked fine... but once it dropped below 3.8 volts it would no longer retard the spark... not sure why???

I put together a new battery set up that has completely solved my problem...

I have a 7.2 volt battery for a kenwood two way radio that I soldered a lead to...
now the CH Ignition needs to have between 4.8 and 6 volts, so 7.2 was too high...
I picked up a 5 volt 1 amp voltage regulator at radio shack for $2.99 and soldered it in-line with 2 other leads to lower to voltage down to just under 5 volts...
now I have a battery pack that kept my engine running for 4+ hours @1300rpm on the bench and still had 6.1 volts left in it when I shut her down... YAY!!!

below are the pics I took of the battery pack and in-line regulator just before hooking it up to the ignition..
the last two pics are a little dark but they show the voltage of the battery and then the voltage of the regulator output...


[link=http://home.insightbb.com/~littlechiefers/battery/DSC00233.JPG]Image 1[/link]
[link=http://home.insightbb.com/~littlechiefers/battery/DSC00234.JPG]Image 2[/link]
[link=http://home.insightbb.com/~littlechiefers/battery/DSC00240.JPG]Image 3[/link]
[link=http://home.insightbb.com/~littlechiefers/battery/DSC00241.JPG]Image 4[/link]
[link=http://home.insightbb.com/~littlechiefers/battery/DSC00245.JPG]Image 5[/link]
[link=http://home.insightbb.com/~littlechiefers/battery/DSC00247.JPG]Image 6[/link]

What is the Raido Shack part number?

it has two numbers on it

"276-1770" at the top of the package and "7805 +5VDC" for the descrpition

A 4 cell nicad is offically empty at 4.4v, in other words even though the cell still has voltage it has no amps left. The low voltage also effects the timing chip.
WHICH is why the specs call for 4.8-6.0v for operation

Thanks Terry...

I forgot to add... the voltage regulator can take up to 35 volts on the input side and still only put out about 5 volts to the ignition....

You could have as much as 2 car batteries wired in series (24v) and still only get 5 volts at 1 amp (1000 mAh) output... Cool huh?

don't know how much current the CH draws but i doubt it is low enough to use that regulator without a heat sink. it's also not considered proper design practice to use the LM7805 without a pair of caps. a pair of tantalums would work fine and be very compact. also important is the 2-2.5 volt dropout but with 6 cells you should be fine.

and $2.99 for a 50 cent part??? but then i guess that's what you have to pay for the convenience of picking one up on your way home from work.....

so if it works for you, great! but do keep an eye on it just in case.


dave

Zagnut, could you make up a little schematic for us for a reliable, simple, cheap, regulator using this part from Radio Shack?? They make them, but like you say, it's irritating to pay $30.00 for a couple bucks worth of components....

Thanks!
AV8TOR

I second the motion.

I'm just about ready to go with my Mr. Mulligan with a CH ignition.

Why make things hard??. Use a 1650 NiMh with 4 cells, runs about 3 hr. on a CH ignition. Then there is always a field charger if you need more than 15 flights a day.

It's just that what I normally do is throw a couple of older 600 mah flight packs together in parallel to make up a good ignition flight pack. Works great, but it's a little heavy (and large) on some of these lighter weight/smaller airplanes I convert to "converted" gassers. I have a couple of nice lightweight 1200 mah LiPoly packs I would love to use, but the voltage is of course too high at 7.4 volts. That's why I have the interest in an inexpensive voltage regulator. I did buy one of the more expensive ready made ones, but if I could make one myself much cheaper, I would use that for the ignition pack, and my "high dollar" one for the flight pack.

AV8TOR

You know I did notice that it got a bit warm but I just attributed that to being run for 4+ hours... I don't believe it got hot enough to need a heatsink...

Here, I used my home electronics book (I just tinker with this stuff.. I'm no expert) took me about an hour... You can have between 5.3 to 24 input voltage, with a 5V 1A output...

i'm just not a fan of using regulators unless absolutely necessary. linear regulators have to have huge heat sinks to handle the current needed for a bunch of big servos and just waste the dropped voltage as heat. an efficient switching regulator that can handle the current also gets so big and heavy that you may as well go back to a regular 5 cell pack...also costs big bucks...

for flight packs i and some others have been using 2 cell li-pos without regulators. in reality they put out less than a volt more than a fresh 5 cell pack and most servos take it just fine. those that don't seem to like it just get a diode added to the positive lead to drop the voltage a bit. receivers have no problems as they're regulated internally.

but since we're talking ignitions it gets a lot more doable due to much lower current and the fact that a failure just means landing dead-stick...and we all know how to do that

google "LM7805" and you'll get a bunch of data sheets with schematics for their proper use. normally just two caps are needed and their specs aren't to important. but a much better choice IMO would be an LM2940 low-dropout regulator that only needs an input of 0.5 volts higher than the output, about $1.50 at digikey. same exact schematic as the 7805 but here it is very important that the cap on the output meets the specs in the data sheet. searching digikey i find that all the leaded caps that fit are $$$ but part #478-1759-1-ND for $1.20 would do nicely. this is a tiny SMT chip that could be soldered right across two leads of the regulator.

another choice might be a switcher like this: http://www.dimensionengineering.com/DE-SW0XX.htm ready to use, good price and the voltage dropped isn't just wasted as heat but turned into added capacity. and best of all is that they don't rape you with their shipping costs.


dave

If you just want to drop the output voltage of a 7.2V 6-cell pack down to around 6V, why not just wire up a 1A diode inline with the battery pack? Any of the 1N4001, 4002, etc. will have a forward voltage drop of about 1.0V. Twist 2 of them in parallel to get 2A capacity if you're really worried about current draw with that hot-rod gasser of yours that can spool up to 15,000rpm.

Really though, why carry the weight of a 6cell pack when you don't need it? Remove 1-cell and be happy. A while back, I bought a whole bunch of Nokia cell phone battery packs from www.allelectronics.com that are 6cell NiMH 850mAh. I break out the cells, which are rectangular and look like bricks, and make RC packs out of them. Work great.

Voltage regulators have their uses obviously, but I don't buy all that hoopla about expensive LiPo packs and shiny regulator heatsinks. People buy 'em because they look sexy inside a 40% Yak and because the Pros use them. For me, direct cconnections and heavy-duty switch/connector is the best policy.

Fully charged NiMh can hold 1.5V per cell (for a very short period) that means you may start with much higher voltage than you wanted.

I use home-made 7805 based voltage regulators for my engines and I'm very happy with that. They cost and weight nothing, and with 2 cells lipo they don't need a heat sink. I do this for weight - 2 lipos are almost twice lighter than 4 NiMh. While making my own regulators (7805 + 2 capacitors) I include small piezo buzzer (like this [link=http://www.kingstate.com.tw/product/kpe-242/kpe-242.gif]KPE-242[/link]) that costs and weights almost nothing. Thanks to that I can hear when ignition is 'hot'. Buzzer is on the 5V side so I know that battery, switch and regulator are working fine when I flip the switch. And after landing and killing the engine the beeping reminds me to tun the ignition off.

RS is really expensive, but I got my parts from local electronic store (5-pack of 7805 for 2 dollars). The most expensive is a power switch itself .

RysiuM

That over-voltage is of no practical concern, as it slides off the discharge curve very quickly. Most often, it is not even present by the time you switch on the system and apply a load to it. I have checked fully charged pack voltage with a loaded ESV, and I have never seen the fabled 7.5V (1.5V per cell). I use a field charger to top off every other flight or so, and I have not had any problem with the 5cell packs I use.
I use a super-bright LED instead. It draws less than 20mA and can be seen in direct sunlight. I use the same LED setup for on board glow drivers. At this point, I tend to trust my eyesight more than my hearing.

Ok well.... does anyone think that there are any viable uses for a voltage regulator? Maybe not for planes alone but for other RC hobbies as well? Cars, Boats?