ICM7556 Monostable Touch Switch doesnt work

I have a touch-activated circuit (5V power source) that works fine with an NE556 chip, driving the Output up for about 8 seconds (timing circuit consists of a 4.7microfarad cap and 1.5M resistor), driving an NPN transistor that powers an LED (see attached circuit). As a monostable circuit, after 8 seconds the Output drops to 0V until I ground the Trigger again. When I replace the NE556 chip with the low power CMOS ICM7556 (this circuit will run on a battery and I need to draw as little current as possible), the Output stays high for the 8 seconds, and then after a barely visible drop in voltage (Voltmeter hardly moves) Output goes high again, acting like it's an astable instead of monostable circuit.

I understand that CMOS versions are much more sensitive, and I am wondering if the circuit is being activated by a stray signal, etc. I am currently only using one of the 556 timers, and read somewhere that maybe the open pins on the second timing circuit could be interfering with the first circuit.

I imagine it is my lack of electronics experience (especially with CMOS devices) that is the main culprit, but any help in figuring out how to get the ICM7556 to act like a "normal" 556 would be most appreciated!

The most obvious things that stand out are the resistor values. 220K is way too high for the transistor especially if the signal is coming from a low current device like a 7556. Try something lower maybe about 10K. You could also increase the 4.7uF capacitor and decrease the 1.5M resistor to get the same RC time constant.

Finally, its always good practice to ground the control pin through a 10nF capacitor.

Edit: You might also want to move the LED to the collector side of the transistor. I'm not sure what effect having a voltage drop between emitter and ground would have.

There is also no resistor in the discharge path. Discharging a 4.7uF capacitor repeatedly through the device will probably destroy it.

The trigger input should be pulled high via a 10K or so resistor. Otherwise it is floating when you don't ground it.

Bob