Well, using MOSFETs with diode-ORing won't work terribly well either - you'd need pull-down resistors on each gate to make sure that they are turned off when they are supposed to be off.

Transistors and diode ORing just won't work for this; ran into this very problem with a project I was helping OxboRene with about a year ago. At that time, I determined that 3.9k was the minimum size for the output resistors and still maintain a valid logic '1' level with the cascaded OR gates. I used 5.1k for these schematics to have an extra margin of safety.

But like I speculated above, I think the EL inverter box probably requires a couple of hundred mA (or more) during start-up. Some vendors say that you can't use rechargeable batteries for their EL units, leading me to reach the above conclusion.

I'd mentioned the 2N7000 a couple posts ago, now I'm thinking those will be inadequate. Not sure that even the IRLD024s will work. IRLU024's would; these are 3-legged critters in a TO-251 case (IPak), sort of like a small TO220 package.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRLU024NPBF-ND

They are not dissimilar to IRLR7807's that I sent to you, Bill - except these have long terminals instead of pre-formed leads.

 

Thanks guys
Bill, I understand Wookies circuits, I was just trying this because I dont have any gates lying around and didn't have time to ship them.
Norhtern Indiana competition is saturday but if we go on to state I'll definatley use ont of these.

Quite a bit of what you two just said went over my head, what exactly is a diode OR gate (is it what I was trtying to make?) and what is a diode-Oring?

In Wookies schematic, what are the output resistors for?

And for the transistor, is te maximum input current on the base the most that can flow between the collector and emitter? Because the chip is powered separatley and each of the EL wire units have their own power supply.

Also, Bill, I simply don't have the time at the moment to read through the posts you have suggested to me, I really hope that I will have some time next week if my plasma speaker preoject goes smoothly (it probably won't) and over spring break (if we have one) I plan to hide from the world for a week and read through your stuff and a good chunk of the E-book, finish off the Make: Electronics book, and just educate myself over all the stuf I've been meaning to get around to doing but just haven't had time to.

 

Thanks guys
Bill, I understand Wookies circuits, I was just trying this because I dont have any gates lying around and didn't have time to ship them.

Well, it would take a lot of transistors to do what you need to do, and I'm afraid you're out of time for that.

Quite a bit of what you two just said went over my head, what exactly is a diode OR gate (is it what I was trtying to make?) and what is a diode-Oring?

If you have two diodes with the anodes as the inputs, their cathodes tied together with a resistor to ground, you have a diode OR gate. If either/both input(s) is/are high, the output will be high - less the diode drop, of course.

In Wookies schematic, what are the output resistors for?

I'm showing 5.1k resistors connected from the OR gates (various places) to the MOSFET gates. In case one of the gates gets shorted to the drain (a common failure mode), the resistors will protect the rest of the circuit from damage, allowing the remainder of the circuit to function normally if possible.

And for the transistor, is the maximum input current on the base the most that can flow between the collector and emitter? Because the chip is powered separately and each of the EL wire units have their own power supply.

For operation in the saturated region, Ib needs to be the desired Ic/10. However, the 4017 can't source more than a few mA's before the output level
falls into the "no-man's land" territory referred to as the "indeterminate" area; neither a logic 1 nor 0. You want to keep clear of that area, or your results will be indeterminate as well.

 

Does EL wire unit have only two connections? Can you supply any additional information. Why are you using Q0- remember that it is high when 4917 is reset.

 

What is wrong with this modification? Minimum of one mA per base, only one diode drop per base, 4017 outputs not requined to support other logic functions. Emitter follower at Q3 probably not needed.

 

Bernard,
The emitter follower idea would source more current to the bases - but I'm thinking that the EL supplies will probably need 100 or more mA's to start up.

For the EL supply switches, 10mA on the transistor base would allow 100mA collector current - so every 4017 output would need an emitter follower; otherwise the logic level would drop too much.

 

Thanks Sgt. Not knowing specs on ELs, left collectors open for future additional drivers. Dug out some measurements on HFC 4017 by ST:
Supply V Load Ω V out I mA [ 9 V Alk. Battery ]
8------ 4048--- 7.5--- 1.8
8------ 2221--- 7----- 3.1
8------- 872--- 6.5--- 7.4
7.9----- 439--- 5---- 11.4
7.5----- 213--- 3.5-- 16.4