In Episode 1, we talked about Radiation level dosimeter with pulse output and MCU

To us, engineers with considerable experience in the development of electronics, this module seemed the simplest. When the task is to develop such an element of the device, but which will be reliable and stable, convenient for modern automated mass production, you can not imagine all the nuances – so later it turned out that in reality, everything is more complicated than on paper. Developers rarely share the difficulties and obstacles. We think that this should be interesting and useful for other developers.

We have already got used to the fact that in the market of components you can find everything you need, especially – analog components, which must be manufactured by a serious and responsible manufacturer. Finding such components for the manufacture of DCDC_3V3_400V was not an easy task;
Another mistake – we integrated the first prototypes in one board (not modular). This led to multiple reissues of the full board of the X-ray meter. The modular approach accelerated development;
Attempts to choose cheap components were also difficult. We recommend choosing components from proven manufacturers: expensive, but technologically.

As a result, we got a fairly miniature and economical module DCDC_3V3_400V with the ability to generate high voltage at low input voltage.

Application of the DCDC_3V3_400V module.

We developed this module for use as a power source for a Geiger-Mueller tube. But, according to our concept, we have significantly expanded the range of technical characteristics so that the module can be used in other projects.

Figure 1. GGreg radiation recorder with soldered module DCDC_3V3_400V

Specifications .

Features	Minimum	Recommended	Maximum
Input voltage level	2 Volts	3.3 volts	5 Volts
Output voltage control range	200 Volts	400 Volts	1200 Volts (at 5 Volts at the input)
Current consumption	10 mA	18 mA	20 mA
Load resistance	1 MО	10 MО	10 MО
Input connector	VCC, GND	VCC, GND	MicroUSB
Output connector	High voltage, GND	High voltage, GND	High voltage, GND
Protection	Not provided	Not provided	Not provided
Stability of the output voltage level	± 5% at a stabilized input level	± 5% at a stabilized input level	± 5% at a stabilized input level

Important instructions :

The input voltage is applied to a micro USB or two pins DCC and GND.
To ensure the stability of the parameters, the module is powered through a linear voltage regulator.
When measuring the high voltage level when adjusting its level, use a high-resistance voltmeter (10 Mм) or an oscilloscope. Set the potentiometer to the minimum position before turning on the module. Be careful when measuring and adjusting.
Significant excess of the output voltage can damage the elements that generate pulses to the controller.
The diagram shows the node of the logical preparation of pulses for the correct perception of their MCU. Note that the circuit needs to be adjusted depending on the specifications of the MCU you plan to use.

You can use the DCDC_3V3_400V module not only for the manufacture of dosimeters with Geiger-Mueller SBM-20 tubes, the supply voltage of which should be in the range of 380-480 Volts. There are other tubes that need to be supplied with a different voltage (for example, SI-38G – 550 Volts, SBM-14 – 1200 Volts).

Additionally, we will list several recipes :

To power rare digital gas-filled indicators, the installation of which has recently become fashionable again.
Fans of quality sound claim that the use of rare tube amplifiers provides better sound compared to semiconductor. Using this module, low-power tube devices can be powered by batteries or accumulators.
The module can be used in devices for protection against mosquitoes, in ozonators, etc.