Egodriver Double voltager

[teknoman2]

I took off max1044 and I measured the current draw (from ground to output of the resistor).

Also I changed battery to have more accurate resuslts cause the last one was dying.

My battery voltage is 9.4v and my voltage across the resistor is 9.0v,
so I have 4mA current draw.

When I measured pin 8 of TL082 I have 7.7v when its off and when its on 9v,

I dont understand why is this happening.

[RobA]

Do you have the voltages measured at the pads of the switch (all three pads)?

I'd first look for solder bridges around the switch and check for possible issues in the switch itself as a first step.

[teknoman2]

When the swith is on I have :
pin1=8.8v
pin2=8.8v
pin3=17v

When its off
pin1=6.7v
pin2=10.5v
pin3=10.5v

[RobA]

But your battery is at 9.4V and the output side of the 100Ω is at 9.0V in both switch positions?

[teknoman2]

I just saw Fred Briggs Super OCD schematic

http://1.bp.blogspot.com/-mdmZKzXJusA/T00EjAPiDyI/AAAAAAAABA8/gwhJo9nX90Y/s1600/briggs_super_ocd.jpg

It has pins 5 and 6 open,
so I measured having 5 and 6 open.
When its onn
pin1=8.8v
pin2=8.8v
pin3=17v

When its off
pin1=7.3v
pin2=12.1v
pin3=12.1v

[teknoman2]

But your battery is at 9.4V and the output side of the 100Ω is at 9.0V in both switch positions?

I dont have the same voltage on both positions,
when its on is 8.9v and when its off is 6.7v

[teknoman2]

I believe the 6.7v measurement is strange.....

[RobA]

You definitely want pin 6 not connected as it's the low voltage pin and you are above 3.5V. All of the spec sheets show pin 5 connected to ground for the voltage double circuit.

What happens when you have pin 6 lifted but pin 5 in place?

[RobA]

I believe the 6.7v measurement is strange.....

Yes, me too. It makes me think that either there is a short or the chip or switch is bad.

[teknoman2]

Now I am at work and I dont have another max1044 but when I return back home I will change it,

I lift pin 6 and now I have 8.8v across resistor when its on

and 7.3v when its off (21mA current draw is too much I believe).

My switch woltages are
On=8.8v, 17v, 17v.
Off=7.3v, 12.1v, 12.1v.

[teknoman2]

I just realise that when I take out max1044 the current draw is the same 4mA.

In both positions of the switch I have 8.8v across the 100R resistor.

If there were a short probably the 7.3v measurement will reappear even when the max will still missing,

am I correct?

[RobA]

Depends on where the short is.

I'm breadboarding this with a MAX1044 to see what my voltages look like. I'll let you know when I get it measured.

[teknoman2]

Thanx mate,

if finally gonna  solve it I will send you an pcb of this one.

Again thank you for your time.

[RobA]

Hey, no problem. I have an ulterior motive anyway. I ordered a couple of the MAX1044's a bit ago and haven't had a reason to put any thing together with them yet. I wanted to check them out to see where the oscillator frequency noise was on them. On all of the TC1044SCP and 7660's I've tested so far the oscillator was in the audible range even with the boost pin on. The only charge pump I've found that consistently performs well is the LT1054. So, as soon as I give you these voltages, I'm going to scope the rails with the MAX1044 in place and see where it's at.

I built just the power supply section of your circuit on breadboard. The current draw from the MAX1044 is tiny, ~4mA. So, you really shouldn't see much in the way of a voltage change at the output of your 100Ω resistor with the 1044 in place or out.

First off, on my breadboard, your schematic for the power supply works just like you want it to. The switch flips between 18V and 9V perfectly.

I didn't connect pin 6 to ground and I don't really want to try (at least not yet) as it might damage the device. I might be up for a little destructive testing after I check out other areas of the charge pump .

My input is 9.41V and 9.38V after the 100Ω.

The output of the switch is either 9.38V or 18.02V.

There is no change on either side of the switch with position of the switch.

IC voltages:
Pin 1 : 9.38V
Pin 2 : 4.69V
Pin 3 : 0V
Pin 4 : N.C.
Pin 5 : 0V
Pin 6 : N.C. but at 5.06V
Pin 7 : N.C. but at 7.58V
Pin 8 : 9.38V

I'm using Nichicon PS series 10µF caps. They are a low ESR cap and this does seem to help a bit with charge pumps. It shouldn't be significant for your issue. But it might help the MAX1044 in the frequency area I'm going to test next. One other thing to note is that if I move to using 1N5817 diodes, the output voltage goes up to 18.68V.

[teknoman2]

I just double check again my voltages and I found that something odd,

I measure ground voltage 0.03-0.1V

Is that normal?